Network Technical Documentation

version 3.0.52

by Wayne Heyward aka Midnight Tree Bandit
Updated for Net37, WSS
Updated for Net52, WSS

Copyright (c) 1998-2016, WWIV Software Services
Copyright (c) 1995, Wayne Bell

Table of Contents



A. History

Back in 1989, Wayne Bell released the first technical documentation covering the technical workings of the WWIV networking software. While much of the information in that document is still relevant now, much has changed since 1989. The Group structure has been added, support for more message types, and support for preprocessors to the packet tossers has been added.

So in late 1992 or early 1993 Wayne asked for volunteers to rewrite the Network Technical documentation. No one spoke up. Then in March I started providing WWIV support on the GEnie information service, and some people started asking about getting technical information so they could get their non-WWIV boards to communicate with WWIV networks. Looking around, I found the original doc, and asked Wayne if anyone had answered his call. As it turned out, I became the volunteer. After much procrastination and "How's the doc coming?" from Wayne, here it is.

B. Purpose, Limitations, and Other Info

The purpose for this document is to explain WWIV based networking interface for those who wish to write software which communicates with WWIV based systems, either independently or as an extra utility for the existing NETXX software.

The documentation that you are reading now is more an expansion and clarification of the original docs than it is a total rewrite. Now that the bulk of the work is done, the plan is to update them with each release of NETxx to reflect new features. The information in this document is current as of the Net52 release (NET52).

First clarification: in the context of this document, the term "NETXX" refers to the software for interfacing WWIV-type networks and any network which uses that software.

This documentation assumes that the reader at least:

  • Has a good working knowledge of C and the various C data types and data structures.
  • Has a general familiarity of how file transfer protocols work.

This document is not a replacement for the NetXX Software Documentation. This doc does not describe how to use the network software, only how it works. For instructions on using the NETXX software and familiarize yourself with how to use it, see the documentation, which can be found in the current NetXX release.

A note on the numbering for this document. This is version 3.0.51. The first number indicates that this is a major rewrite from the Midnight Tree Bandit which was a rewrite of the original by Wayne Bell. Unless a major overhaul is done, this is not likely to change. The 0 in the second part indicates that this is the first version of this document. If there are any major changes or additions made, this will be incremented. The 52 indicates that this information is current as of version 52 of the NETXX software (NET52). Minor changes reflecting small interface changes in the NETXX software will cause this number to be changed. This number will not always be the same as the latest version of the NETXX software; if there are no changes in the external interface, this document will not be updated.

Comments concerning this document are welcome as are suggestions for additional information to include, things that could be explained more fully, and so forth. For comments please log a bug on github at

C. Relevant Copyrights and Acknowledgements

This document is Copyright 1994 by Wayne Heyward (aka Midnight Tree Bandit) and updated by WWIV Software Services (WSS). It may be freely distributed provided it is not altered in any way. This is copyrighted to prevent unauthorized (and possibly inaccurate) changes from being made to this document by anyone other than myself or any other appointed by WWIV Software Services ( should I be unable to continue updating this document).

WWIV BBS and the NETXX software (distributed as NETxx) are Copyright 1989-1995 by Wayne Bell and Copyright 1998-2016, WWIV Software Services.

The NETXX interface information and code in this document is placed in the public domain, and may be freely used for the purpose of interfacing with WWIV networks and network software.

I would like to thank Wayne Bell, not only for creating a top notch BBS program that is both powerful and easy to use, but creating a networking scheme that is more painless to set up and operate than any other out there. He has said often that if he knew then what he does now, things would have been different. I cannot help thinking that the result would have been less elegant or easy to use.

I would also like to thank Wayne for his patience over the last year and a half, waiting for me to get this document started. I've fired thousands of questions at him the last few weeks in an effort to make this documentation as complete as possible, and he answered every one.

And finally thanks to Filo, who also provided vital information and advice without which this documentation would be incomplete.


A WWIV network is basically a loose confederation of WWIV BBS systems that use the NETXX (or compatible) software.

The software does not limit the connection structure, so the member sysops can connect to anyone they wish (subject to the rules of their network). For ease of administration, the network may be split up into Groups, each with their own coordinator. Node numbers are an unsigned short int, so that nodes may be assigned a value from 1 to 65535. Node numbers from 32000 to 32767 are reserved for internal use by WWIV.

The following network numbers are reserved: * 32765: Net5x Native FTN Networking * 32766: Net5x Natie NNTP * 32767: Legacy PPP Project/WINS and Net5x Native Internet Email

The lists of nodes are distributed in two sets of files: BBSLIST.NET and CONNECT.NET. The CONNECT.NET file assigns costs to each connection for each system.

Like all BBS networks, the primary purpose is to exchange private mail and public posts between BBSes. The passing of files in binary form, however, is not currently supported by the NETXX software. There are some third party programs and in fact, an entire network which can handle the network transfer of files. All messages also have a maximum size limit of 32k.

NETXX (NET38) and earlier is proprietary software, from WSS, distributed in by WSS. Since NET51, the network software is a new implementation of a subset of this technical specification. It is not related at all in either code or complete functionality to NET38 and earlier.

The basic NETXX software distributed as part of the BBS software. It consists of the following programs:

Binary Description
network A shim to invoke networkb.exe using the same arguments as the legacy networking software.
networkb The WWIVnet transport software, it's implemented using the BinkP protocol.
networkc Similar to the old CLNUP.EXE software by Cerebrum Software. It runs the other network{1,2,3} commands as needed.
networkf Used to "toss packets", aka convert between WWIV Packets and FTN bundles (.SU?) and FTN packets (.PKT).
network The first of the two mail tossers. This one takes the incoming packet received by NETWORK.EXE and distributed the messages within to their rightful places. Local mail goes into LOCAL.NET, while mail passing through to other systems is tossed into packet files for the next hop.
network2 Tosses the local messages in LOCAL.NET. Most are messages for email or local subboards, but there are also network updates, sub REQuests, software "pings," and other special purpose message types. It also has the ability to call on third-party preprocessors for special handling of certain types of messages.
network3 processes all the network updates that come in. This helps determine what routing off-system mail will take.

Each WWIV network also has its own special encoding and decoding programs for handling of updates and network mail from the Network Coordinator and Group Coordinators. These are the DEmmm.EXE files (mmm corresponding to the message type). The DEmmm.EXE cannot be replaced, so any network2 replacement must be able to recognize the need for calling the appropriate DEmmm.EXE, as described below.


Starting with With Net51, connections happen outside of the network software. You use networkb to call out to another node or use networkb directly or use a proxy like wwivserver or wwivd to listen on BinkP and spawn networkb on demand.


The most important component of any network is the mail file, which contains all the public posts, email, and network information which makes the BBS network what it is. NETXX mail files consist of a series of mail packets, each with its own header segment describing the type and size of the packet.

There are two types of mail files in NETXX, each similar but processed differently. The netmail file is the file received from another system, and contains packets destined for that system as well as other systems in the network (if the BBS has more than one connect). The local mail file contains the packets from the netmail file which are destined for the BBS only.

A. Message Header

Each message sent through the network has a header. The header tells which user/system originated the message, where it is to be sent to, the type of message, and other information. The structure of the header is:

struct net_header_rec {
  uint16_t  tosys,    /* destination system */
           touser,     /* destination user */
           fromsys,    /* originating system */
           fromuser,   /* originating user */
           main_type,  /* main message type */
           minor_type, /* minor message type */
           list_len;   /* # of entries in system list */
  uint32_t   daten,    /* date/time sent */
             length;   /* # of bytes of msg after header */
  uint16_t  method;    /* method of compression */

Each header is 24 bytes long. The fields, in detail, are:

tosys, touser

The destination of this message (system number and user number, if applicable). The touser field will be zero in all cases except for email (main_type==2) and SSMs (main_type==15).

fromsys, fromuser

The origin of the message (system number and user number). This contains the user number/system number combination of who actually wrote the message.

main_type, minor_type

The type of message this is. The main type stores the actual type (email, post), and the minor_type is used to specify what sub-type it is. For example, the main_type for a post is 3. The minor_type is then used to specify what type of post it is, what subboard the post is to go on to. A list of main and minor types is found in section IV(D), below.


The time the message was sent, stored in unix time, as the number of seconds since Jan 1, 1970.


The length of the message. This includes any information between the packet header and the message itself, such as the sender's name, message title, and so forth. Note that the length does not include the node list indicated by list_len.


If the file is encrypted or source-verified, this describes the type of encryption used. This will tell NETWORK2 (or other local mail tosser) which DEmmm.EXE to execute. DEmmm.EXE is explained in more detail in the next section, below.


Some messages need to go to more than one system. For example, networked posts may go to over 20 different systems. It makes no sense to have a separate copy of the message for each destination system, so the same copy of the header and message is used. (This is referred to as "stacking" the message). The list_len specifies the number of destination systems listed. If list_len is non-zero, then the touser and tosys fields are ignored. The list_len is not used for e-mail to a user (main_type is 2 or 7).

When a message has only one destination system, the destina tion system is stored in tosys, and list_len is zero. If there are two or more destinations, then tosys is 0, and list_len holds the number of destination systems.

When list_len is non-zero, the list of destination systems is stored immediately after the header, but before the actual message itself. The length of the list is not included in the length field in the header; the length stored in the header is the length of the message only.

Each entry in the destination system list is two bytes long, and is stored in the little-endian format (x86 default format).

For example, if a post is destined to system 1, the tosys field will be 1, and list_len will be 0. If the post is destined to systems 1 and 2, tosys will be 0, list_len will be 2, and there will be 4 bytes between the header and message. The bytes will be: 01 00 02 00 (remember, byte-reversed format). The rest of the header will be the same for both messages.

A packet thus consists of a net header, a destination list (if any), and the text of the message. The length of a full message packet is thus: 24 + 2*list_len + msg_length.

The message text (the part following the header) for a post or email begins with information intended for the message header shown when the message is displayed. Each piece of information is followed by a carriage return and line feed (cr/lf) character to separate it from the next except for the message title, which is followed by a NUL character. For most posts and email, that information is:

Message Title

Whatever title the user gave to the post.

Sender name

usually the name and number of the user who wrote the message with the system number, in whatever format the sending BBS uses.

Date string

Formatted date the post was written, in whatever format the BBS uses.

So the message header format for most posts and email would be TITLE<nul>SENDER_NAME<cr/lf>DATE_STRING<cr/lf>MESSAGE_TEXT.

Some main_types have other information, as noted in the main_type descriptions in section IV(D).

B. Mail File Processing

A NETXX file is simply several packets appended into one file.

Once it has been received the mail file should be processed following these steps:

  1. Open the file, and set the current message pointer to the beginning of the file.

  2. Read in the net header (24 bytes).

  3. If list_len is non-zero, read in the list following the header (2 * list_len bytes).

  4. Read in the message itself (length bytes).

  5. Process the message.

  6. If not the end of file, go to step 2.

To ensure the integrity of the mail file, an initial pass over it should be done. This pass would step through each packet in the file, reading each header and making sure no packets are truncated. If the file ends in the middle of a packet, then it is obviously corrupted and cannot be processed properly. At this point, either throw away the whole file or remove the truncated packet and process the remaining packets.

During the packet tossing, each packet needs to be marked as processed. Thus, if analysis is interrupted before completion, the packet analyzer can skip over those packets already processed when run again. To mark the packet as already processed (or deleted), set the main_type to 65535. Any packet with a main_type of 65535 should therefore not be processed.

The analyzer should follow these steps when processing each packet:

  1. If main_type is 65535 (deleted), skip the message.

  2. If list_len is non-zero, do steps 3-6 for each entry in the list, substituting that entry for "tosys"

  3. If tosys is this system, process the file locally (in the case of network1, the message is copied to LOCAL.NET for processing by the local packet processor).

  4. If tosys is an unknown system or unreachable, put the packet in the dead mail file.

  5. If the next system to forward the packet to ("next hop") is the system that the message was last received from, put the packet in the dead mail file. This prevents messages from looping

  6. If the tosys is okay, put the packet into the file that is to be sent to the next hop.

Of course, it is more complicated than that. If list_len is non-zero, all destination systems should be processed before the message is stored anywhere. This way, if the message has 10 destinations, each of which has the same next hop, only one copy of the message will be printed out, that packet with 10 systems in its destination list. Likewise, for a system with more than one connection, if a message has 4 destination systems going through one next hop and 3 going through another, one copy of the message will go into each hop's file -- one with four systems in the node list, the other with the remaining three.

The dead mail file is reprocessed whenever a network update (new BBSlist or connection list) is received.

C. Local Mail Processing and DEmmm.EXE

Processing of local mail packets should be similar to processing of incoming netmail packets. The main difference between netmail tossing and local mail tossing is that the main and minor types are ignored during netmail processing, and the list_len and node list are ignored (since there won't be a list on local mail).

  1. Open the file, and set the current message pointer to the beginning of the file.
  2. Read in the net header (24 bytes).
  3. Read in the message itself (length bytes).
  4. Process the message. This is done according to the main_type and (if applicable) minor_type of the message.
  5. If not the end of file, go to step 2.

A few main_types (noted below) cause return messages to be generated to go back out to other systems. The local mail file analyzer should place these into an interim mail file that will be processed by the netmail file analyzer after local mail processing has been completed. The NETXX local mail analyzer (network2) puts these messages into P1.001 or P2.001. Then network1 analyzes this file and places them into outgoing netmail files for the system's connections.

Some types of messages that contain network related files such as updates to the nodelists and connect lists and email to all sysops from the NC. For the sake of network security, these messages have a source-verification signature at the beginning (using, for example, RSA or a similar algorithm). There are several "methods" used to handle these messages, and each requires a decryption program, or DEmmm.EXE (where "mmm" is the encryption method, as listed in the 'method. field of the net header). These DEmmm.EXE files MUST be supplied by the NC of each network, and each network's DEmmm.EXE are unique to that network. That is, NETXX's DE1.EXE will not handle method 1 messages from WWIVLink, nor vice versa.

When a message is encountered with 'method!=0', the following steps are taken:

  1. The local packet analyzer writes out the text of the message (no header or node list) to a temporary file (TEMPDE.XXX) in the data directory for the relevant network.
  2. A command line for calling the appropriate DEmmm.EXE is created using the C command "sprintf(cmd, "de%u %s/", nh.method, net_data);" ('nh' is a structure of type net_header_record, 'net_data' is the network data directory). The command is then executed.
  3. The DEmmm.EXE program is then responsible for reading the TEMPDE.XXX in from disk, deleting it, then attempting to decode it. Two things can then happen: a. If the TEMPDE.XXX fails decoding (bad CRC), DEmmm.EXE just exits (returning to the local packet analyzer). If the analyzer finds the TEMPDE.XXX file does not exist, the message is deleted and the program goes to the next packet. b. If the CRC checks out in the DEmmm.EXE program, it writes out the decoded text into a new TEMPDE.XXX file and exits. The local packet analyzer reads in the data from that file and replaces the text of the message with that, then goes ahead and processes the packet as determined by main_type.

Network operators who wish to write EN/DE programs for their own netwide messages may wish to consider using the RSAREF library to develop their own source-verification scheme.

D. Main and Minor Message Types

The main and minor type of each message determines how it is processed (where it goes, whether it's a sub post, email, or network info, etc.). The analyzer reads the message header in first to get the main and minor types, then performs the operation indicated by those fields.

Here is a list of the main_ and minor_types, along with the WWIV BBS #define name and descriptions of the processing required. Encoding method is assumed to be zero unless otherwise noted. Note that while these descriptions concern analyzing local mail packets, they also apply to how to create outgoing netmail packets.

main_type 1 (0x0001) -- main_type_net_info

These messages contain various network information files, encoded with method 1 (requiring DE1.EXE). Once DE1.EXE has verified the source and returned to the analyzer, the file is created in the network's DATA directory with the filename determined by the minor_type (except minor_type 1).

Minor Type Description
0 Feedback to sysop from the NC. This is sent to the #1 account as source-verified email.
1 BBSLIST.NET -- Node list.
2 CONNECT.NET -- Connections list.
3 SUBS.LST -- List of subboards ("subs") available through the network. This has been replaced by main_type 9.
4 WWIVNEWS.NET -- An electronic magazine of sorts distributed within some networks, usually monthly.
5 FBACKHDR.NET -- a header file added to network update reports for the network.
6 Additional WWIVNEWS.NET text -- appended to the existing WWIVNEWS.NET file.
7 CATEG.NET -- List of sub categories. WWIV's sub setup facility uses this list so the sysop can specify what category a netted sub falls into. The network's SUBS.LST compiler uses this information for compiling the subs lists sent out as main_type 9.
8 NETWORKS.LST -- A list of all current NETXX type networks.

This message type is source-verified. That is, there is a digital signature at the beginning of the message text which is decoded by the DE1.EXE to verify that it has come from a "legal" source. This helps make sure that the network info will only come from the Network Coordinator. If the source- verification fails, the packet is discarded.

main_type 2 (0x0002) -- main_type_email

This is regular email sent to a user number at this system (see tosys and touser, above). Note that this type of mail should only be received by systems that assign numbers to users (WWIV, VBBS, etc.). BBSes in a WWIV network that only identify users by name (PCBoard, RBBS, etc.) can only receive email-by-name (see main_type 7, below). Email has no minor type, so minor_type will always be zero.

Processing of the email is straightforward. The analyzer looks for the user number indicated by the touser field. If the number exists and the user has not been deleted from the BBS, the message is written into the email file, addressed to the user indicated. If the number does not exist or the user at that number has been deleted, the packet is deleted without processing. Alternatively, the analyzer may generate a return message (as email) to the sender telling him that the mail was not delivered and quoting the message back to him.

main_type 3 (0x0003) -- main_type_post

NET51 and later only supports type main_type_new_post.

main_type 4 (0x0004) -- UNUSED

main_type 5 (0x0005) -- main_type_obsolete_pre_post

NET51 only suppors type main_type_new_post.
text (and the list_len field modified reflecting the addition of the node list). If the file cannot be found, the analyzer assumes the BBS does not host the sub and deletes the packet.

Many WWIV sysops use a feature of the software known as network validation ("netval"). When a sub is set for netval (this is found in the SUBS.DAT record for the sub), the analyzer does not send the post out to the network. The sysop must validate the post on the BBS, at which point it is sent out by the BBS. This also applies to pre-posts for main_type 26 (main_type_new_post).

main_type 6 (0x0006) -- main_type_unused_external

main_type 7 (0x0007) -- main_type_email_name

The other email type. The touser field is zero, and the name is found at the beginning of the message text, followed by a NUL character. Minor_type will always be zero.

When this type of packet is encountered, the analyzer gets the name from the beginning of the message text and searches through the BBS's user list to find the specified name. If it is found, the message is written into the email file for the BBS. If it is not, the message will be deleted or a return email may be sent back to the sender, explaining that the message was not delivered and quoting the email back.

The destination user's name is prepended to the beginning of the message text, followed by a NUL, then the rest of the usual message header info and the message text. The message header info at the beginning of email-by-name messages is thus


main_type 8 (0x0008) -- main_type_obsolete_net_edit

main_type 9 (0x0009) -- main_type_sub_list

Networks with large subs lists (over 32k) break them up into parts and send the set out under this main type rather than the subs.lst type under main_type 1. The minor_type indicates the part of the subs list.

When the analyzer processes this type, it creates a file in the appropriate network directory and copies the message text into it. Minor_type zero creates the file SUBS.LST, and all other minor_types create a SUBS.x file where 'x' is the minor_type.

main_type 10 (0x000a) -- UNUSED

main_type 11 (0x000b) -- main_type_not_implemented_group_bbslist

main_type 12 (0x000c) -- main_type_not_implemented_group_connect

main_type 13 (0x000d) -- UNUSED

main_type 14 (0x000e) -- main_type_not_implemented_group_info

main_type 15 (0x000f) -- main_type_ssm

WWIV BBSes also send out small messages, known as "SSMs", across the network. These are little one-line messages generally telling users when their mail has been read and so forth. Some BBSes have been modified to send other types of messages. At any rate, main_type handles these small messages. Minor_type is always zero.

Like email, the analyzer searches for the user number in the BBS's user list. If found, the message is written into the SSM file for the BBS. Since this is a feature most non-WWIV systems do not support, they can be ignored.

One feature of WWIV networking is the ability fpr network sysops to send "REQs" to the hosts of subs, enabling them to automati cally subscribe to and drop subs they belong to. Main_types 16 through 19 handle REQs and their responses.

main_type 16 (0x0010) -- main_type_sub_add_req

This is for requests to add the sending system to a sub's subscriber list. Minor_type will be the numeric sub type, or zero for alphanumeric sub types. For minor_type==0, the sub type (followed by NUL) will be the message text. Otherwise, there should be no message text (if there is, ignore it).

When this message type is received, the analyzer should search for the subtype's subscriber file (N[subtype].NET for WWIV systems). If the file is found, the system number of the new subscriber is added, if it is not in there already. If the add is successful, it will then look for a text file in the data directory (SA[subtype].NET for the NETXX software) that contains information the sysop wants to send back to the subscriber. A type 18 message is sent to the subscriber indicating status of the add request (see below) and including the text in the SA[subtype].NET file, if one is found. If the add is not allowed, the analyzer looks for SR[subtype].NET and sends that text back to the requester. If the add is otherwise unsuccessful, the type 18 message will include the status and a short explanation of why the add was not succcessful.

main_type 17 (0x0011) -- main_type_sub_drop_req

This is the same as a main_type 16 message, except that it is sent by a subscriber wishing to drop a sub. The minor_type is determined the same way as main_type 16. There should be no message text, but if there is any, it is ignored.

Processing is similar to a type 16 message. The analyzer searches for the subtype's subscriber file, and upon finding it removes the subscriber's system number from it, if it is there. Status of the drop request is returned to the sender in a main_type 19 message, with a short message appended that explains the status.

main_type 18 (0x0012) -- main_type_sub_add_resp

This carries the status response to a main_type 16 (sub add request). The minor_type is determined the same way as type 16 message. The first byte of message text (after the subtype, if minor_type==0) is the status of the add request. Possible status byte values are:

Statsu Byte Description
0 Subscriber added successfully.
1 This system is not the host (N[subtype].NET not found).
3 Not allowed to add subscribers automatically.
4 System number already there (can't add it again).

When received, the processor will send the message text mentioned in the main_type 16 description (minus the status byte) to the sysop as email.

main_type 19 (0x0013)- main_type_sub_drop_resp

Similar to main_type 18, this carries the response to a sub drop request, with the minor_type following the same conventions as above. This also carries a status byte as the message text:

Status Byte Description
0 Sub dropped successfully.
1 This system is not the host.
2 System number is not there (can't drop it).
3 Not allowed to drop subscribers automatically.

When received, the processor will send the message text mentioned in ther main_type 17 description (minus the status byte) to the sysop as email.

main_type 20 (0x0014) -- main_type_sub_list_info

In many WWIV networks, the subs list coordinator (SLC) occasionally sends out "pings" to all network members.

When this message type is received from the SLC (minor_type 0), the analyzer checks the BBS's sub data file. If there are any subs hosted by the receiving system which are flagged for inclusion in the distributed SUBS.LST, a list of them is returned to the SLC via another main_type 20 message with minor_type==1). When the SLC recieves the reply, it is written into SUBS.INF in the network's data directory (appended if the file exists).

main_type 26 (0x001a) -- main_type_new_post

Subtypes are seven characters -- the first must be a letter, but the rest can be any character allowed in a DOS filename. This main_types covers both subscriber- to-host and host-to-subscriber messages. Minor type is always zero (since it's ignored), and the subtype appears as the first part of the message text, followed by a NUL. Thus, the message header info at the beginning of the message text is in the format: SUBTYPE<nul>TITLE<nul> SENDER_NAME<cr/lf>DATE_STRING<cr/lf>MESSAGE_TEXT.

main_type 27 (0x001b) -- main_type_unused_new_external


So how does the network software know where to send an off-system message, especially if the BBS has more than one connect? FidoNet has its nodelists, and so does NETXX. NETXX actually has two different types of node lists, as mentioned elsewhere. We'll take these separately, then discuss figuring out the routing.


In the beginning of NETXX, there were only two files needed to keep up with the systems in the network -- BBSLIST.NET and CONNECT.NET. Though this is rarely used now, there are still some smaller networks which use these files, so they should be discussed.

BBSLIST.NET holds a listing of what systems are in the network. Each system has an entry, with the systems usually grouped by area code. The format for each system's line: system number (preceded by @), system phone number (preceded by *), max bps rate of the system (preceded by #), system flags if any, WWIV registration number or date of entry (enclosed in brackets), and system name (enclosed in ""). For example, the BBSLIST line for Amber in NETXX could be:

 @1     *310-798-9993  #14400 <  !$     [1]  "Amber"

Most of the system flags after the modem speed indicate the kind of high-speed modem being used by the system. Currently, these flags are:

 | -- Telebit-compatible (PEP) modem.
 < -- USR HST 9600+bps modem.
 > -- Hayes V-Series compatible 9600+bps modem.
 Z -- Zoom V.32terbo (19.2kpbs) modem.
 / -- CompuCom 9600+bps modem.
 ! -- CCITT V.32 (9600bps) modem.
 $ -- CCITT V.32bis (14.4kbps) modem.
 ~ -- V.FAST (28.8kbps) modem.
 ? -- Fax-capable modem (not currently used)

Other system flags used which are not modem designators:

Designator Description
+ The system is a dedicated mail server. That is, it is not a true BBS, only handles the transfer of network mail for an area or region.
\ Fidonet system. Some systems in the network have "gateways" into Fidonet (or Fidonet compatible, such as GlobalNet).
= PCPursuitable system. This is actually not useful since PCPursuit has gone out of business (though there are other similar networks still operating).
_ End node. That is, a system with only one connection.

There can also be one of three flags appearing before the phone number: ^ -- Area Code coordinator (AC). & -- Network Coordinator (NC). % -- Group Coordinator (GC) Note that since there can only be one Network Coordinator, the "&" should only appear once in the BBSLIST.NET file. Also, the "%" is not likely to be seen except in the Group setup described below, since this setup has no Groups.

The first line of the BBSLIST.NET must be a tilde (~) followed by the Unix timestamp (seconds since midnight, Jan 1, 1970) indicating the date and time the file was sent out by the NC or GC.

CONNECT.NET lists the connection costs between systems. The cost listed should be the cost per minute, though for most networks using this system, the rule of thumb is 0.00 for local connects, 0.01 for long distance connects, and more for long distance connects that one wants to route less mail through.

Each entry in the CONNECT.NET file specifies a one-way connection between two systems. The entries in the CONNECT.NET file do NOT need to be in any specific order. The format for system's connection entry is: the system number (preceded by "@"), first connection and cost (separated by "="), second connection and cost, and so forth. Like BBSLIST.NET, the first line is a tilde (~) followed by the UNIX timestamp.

Examples: 1. If there are two systems, numbered 1 and 2, and each can call each other for free, the CONNECT.NET file would look like:

      @1      2=0.00
      @2      1=0.00

Note that the routing analysis software should make sure both ends of the connection have entries referring to each other.

  1. There are three systems, each can call the others for free, the CONNECT.NET file would look like:
      @1      2=0.00 3=0.00
      @2      1=0.00 3=0.00
      @3      1=0.00 2=0.00
  1. If system 3 called the other two for $0.10, the CONNECT.NET file would look like:
      @1      2=0.00 3=0.10
      @2      1=0.00 3=0.10
      @3      1=0.10 2=0.10

In both BBSLIST.NET and CONNECT.NET file, each entry begins with identifying the system number (preceded with @), allowing system entries to take up more than one line -- in larger networks a CONNECT.NET entry can fill more than one line. Everything after the system number identifier up to the next "@", corresponds to that system. Thus, the CONNECT.NET files above could also be listed as:

 @1 2=0.00 3=0.10 @2 1=0.00 3=0.10 @3 1=0.10 2=0.10



Thus, the end-of-line indicator (EOL) should be IGNORED.

Neither the BBSLIST.NET nor CONNECT.NET file need to be in any specific order. There cannot, however, be multiple entries per system in either BBSLIST.NET or CONNECT.NET.

It is possible for a system to have references in one or both of the .NET files, but not be reachable from any other system. For example, two systems may be listed in BBSLIST.NET, and listed in CONNECT.NET, but each can only call the other. No other system in the network can connect with them, so they don't exist, essentially. Also, a system can be listed in BBSLIST.NET, but not have any entries in CONNECT.NET. This usually happens for systems just joining the network, and those systems essentially don't exist either.

It is also possible for one system to call another, but the second system can't call back the first. This is unusual, but valid. Also, the cost of a connection can be different in one direction than it is in the other. This is also valid.

BBSLIST.NET is received across the network as main_type 1, minor_type 1 (1/1). CONNECT.NET is received as main_type 1, minor_type 2 (1/2).

C. Figuring the Routing

There are three ways message routing could be determined:

  1. Each time you need to route a message, find the least cost or shortest path (depending on whether new or old update files are being used);

  2. Each time one of the network programs that has to route messages is run, the least-cost or shortest route to each system is decided; or

  3. Each time an update to the .NET files is received, the least cost route is decided to each system.

Options 1 and 2 are simply not practical. Depending on network size and system speed, it can take a minute or more to analyze the network data files and determine the optimal route. Finding the best route to a specific system requires the same operation as finding the best route to all systems, so option #1 is a waste of time (besides possibly requiring the BBS to have the path- finding code in it). Option #2 holds no advantages over option #3 because it will tie up the BBS unnecessarily.

Therefore, the optimal routes to all the systems in the network should be analyzed only when a network update is received. This routing analysis can be done any way, as long as it determines the best route. The best way, however, could follow these steps:

  1. System records are read into an array from BBSLIST.NET. The array is of struct net_system_list_rec (see below). All fields are filled from the BBSLIST.NET except numhops and forsys, which are set to 65535 and 0, respec tively. For the Group setup, the BBSLIST.NET partial updates (.513-.768) are read in next, and the indicated changes (existing systems replaced, new systems added, systems indicated with "." deleted) are made in the array and in the BBSLIST files themselves. After processing, the partial updates are deleted.

  2. Next, the CONNECT files are read into another array. Since system records may be repeated in the CONNECT files, make sure, when each system record is read in, a check is made in the array to see if there is already an entry for it. If there is, add the connections in the new record to the existing record.

  3. Then, the analysis starts. The analyzer uses the system's callout list (CALLOUT.NET for NETxx) as a base, starting with the first entry and checking each of its connnects, spreading out from there to THEIR connects. This is done for each system in the callout list.

    For each destination system checked, the number of hops found is compared to that entered in the network data array (numhops) and changed if it is less. The forsys is also changed, if that is different. This is for the Group setup.

    If the network is using the old NETXX setup, cost, rather than number of hops, is considered. In this case, when figuring cost, the speed of a connection (highest speed two connecting systems will support) needs to be considered. For instance, two systems connecting at 14400bps at a cost of 0.10 would take precedence over two systems connectiung at 2400bps at a cost of 0.10 (assuming that they are on the path to the same destination system, and all other scosts are equal).

  4. When all systems in the callout list are processed, analysis is complete and the network data array is written to disk. If specified, a piece of mail is then sent to the sysop giving the results of the analysis (for instance, how many valid systems are in the network, how many systems route through each of this system's connections, who the NC and GC and AC are, and so forth).

The data structure NETxx's network3 uses for the network data file is:

  struct net_system_list_rec {
  // system number of the system
  uint16_t  sysnum;
  /* phone number of system */
  char phone[13];
  /* name of system */
  char name[40];
  /* group of the system */
  uint8_t   group;
  /* max baud rate of system */
  uint16_t  speed;
  /* other info about sys (bit-mapped) */
  uint16_t other;
  /* how to get there */
  uint16_t forsys;
  /* how long to get there */
  int16_t numhops;
  union {
    /* routing factor */
    uint16_t  rout_fact;
    /* cost factor */
    float  cost;
    /* temporary variable */
    int32_t temp;
  } xx;

It is encouraged that this structure be used by any NETXX compatible analyzer. Not only is this used by the WWIV BBS software, but some NETXX add-ons also use this file, so supporting this structure will enhance compatibility with NETXX.

The fields: sysnum, phone, name, group, and speed should be self-explanatory.

other -- This is bitmapped, and contains the modem and other information shown in BBSLIST. The bitmap values are (with corresponding BBSLIST flag):

            \    other_fido          0x0001
            |    other_Telebit_19200 0x0002
            <    other_USR_9600      0x0004
            >    other_Hayes_9600    0x0008
            ^    other_area_coord    0x0010
            !    other_V32           0x0020
            $    other_V32bis        0x0040
            =    other_PCP           0x0080
            %    other_group_coord   0x0100
            &    other_net_coord     0x0200
            /    other_compucom      0x0400
            +    other_net_server    0x0800
            ?    other_FAX           0x1000
            _    other_end_system    0x2000
            ~    other_VFAST         0x4000

forsys -- Where to forward messages destined for this system, also known as "next hop". For example, if a message going from system 1 to system 5 passes through systems 2 and 4, then forsys==2. When it is determined that the system is unreachable (listed in BBSLIST but no connections listed), forsys==65535.

rout_fact -- This is the routing factor, but is currently not used by the NETxx software.

cost -- this holds the cost of the call, calculated as the sum of costs for each hop to the destination.

When all systems have been processed, you should have a database containing all systems in the network and how they may be reached. Whenever a packet that is not destined for the local system is processed, the data file is searched to find the system entry for the destination system. If it is not found, then the system is unknown. If the system is identified as unreachable (forsys==65535), the system is also considered unknown.


That about covers all the technical details for designing software compatible with WWIV networks. Now for some things to consider for those wishing to design a NETXX interface for a non-WWIV BBS, or add-ons to existing NETXX software.

A. NETXX Interface Software

The information provided in this document is enough for anyone wishing to write NETXX interface software from scratch. Unless you are writing for a BBS on a non-PC platform (such as Hermes for Macintosh), there is no need to rewrite all of the software to interface a PC-based BBS to a WWIV network. Since the local mail processor (network2) is the only program that writes to BBS message bases, that is really the only one needing replace ment. If any of the NETxx programs are used, it is essential that all of the supporting data files used by that software be present. For details on those files, see the NETXX software documentation.

Some additional programming may be necessary, though. For one, a shell would be useful for executing the various network programs, unless the BBS can be modified to make the calls itself. A batch file could do it, but a program such as Jim Wire's CLOUT makes it much easier. Any shell or BBS modification should follow these steps (filenames in parentheses are programs from NET34 or files created/used by them):

  1. Choose a system to call (or have one specified), then execute the network callout program (NETWORK.EXE). If successful, proceed to step 2. If not, either try again or end processing.

  2. Check for the incoming netmail file (P*.NET). If there isn't one, end processing. If there is one, run the netmail packet analyzer (network1).

  3. Check for the local mail file packet (LOCAL.NET). If there is none, end processing. If there is one, run the local mail packet analyzer (network2).

  4. Check again for a netmail packet (outgoing messages result ing from local mail processing). If there is one run the netmail analyzer, otherwise proceed to the next step.

  5. Check for a BBSLIST or CONNECT update. The most reliable way to do this is to compare the filedates of the CONNECT and BBSLIST files against the filedate of the database file created last time the routing analyzer ran. If one or more of the files is new (or there is a partial BBSLIST update), run the routing analyzer (network3).

If the software cannot be modified to handle these steps, it is probably best to use a front-end such as Front Door or Binkleyterm, then set up events that would run the shell for making the network calls and processing.

The trickiest part is exporting messages from the BBS to a WWIV network file. Possibly the easiest way to pack new messages is to have the BBS write them out to Fido packets (if the BBS is Fido-compatible), then when control returns to the front end, run an event that converts the Fido packet to a WWIV mail file. When doing this, keep in mind that WWIV networks do not have all of the fields a WWIV packet does, most notably the "To:" field.

Another method could be a program that, after the BBS returns control to the front end, scans the BBS's message bases for new messages on the NETXX subboards. This would work best for BBS programs that cannot export Fido messages. In either case, it is important that the netmail file processor analyze the outgoing message file (P.NET) for tossing into the various connection files (S.NET).

Of course, the optimal solution, if possible, would be to modify the BBS software to export the messages directly into a NETXX compatible mail file, and run the other network programs as needed without the shell.

This is probably be a good time to discuss the naming of the incoming and pending netmail files, mentioned in step 2 above. The actual name of the P.NET can vary, depending on NETxx version and what program generates it. NETWORK.EXE receives the file as P1-0-1.NET. The "-0" in the middle indicates that NETWORK.EXE created the file (think of it as NETWORK0). When other NETXX programs generate pending netmail files, the middle number indicates which program created it (network2, the local mail processor, would create a pending netmail file named P1-2-1.NET). The main reason for this naming system is so that we can tell the source of a P.NET file being processed by the netmail analyzer.

The WWIV BBS just creates P0.NET (network email, generally) and P1.NET (outggoing sub posts, generally). Multi-instance WWIV create P.nnn (where 'nnn' is the instance number, such as P.001 for instance 1) while a user is online, but they are renamed to P*.NET after the user logs off.

The network1 processes all of the P.NET files, until none are left. It is important that an alternate netmail file analyzer be able to recognize and handle any P.NET file, not just Pn.NET.

B. NETXX Software Add-ons

There are two possible types of add-ons supported by the NETXX software, both working with the local mail processor.

A common use for external messages is what is known as a "ping," used by the authors of some WWIV network utilities who wish to gain some information about the use of their software. The author sends out a main_type 27 message with the minor_type they are using. If a receiving system is using the software and it is installed properly, it will execute after local mail processing, and process the request in the external message.

The local mail processor also supports use of "pre-processors," generally used to scan the local mail file for certain types of messages before the local mail processor gets to it. One example is JAFO's AUTOSEND, which looks for sub requests and sends out messages from the system's subs to new subscribers. These, also, are described in the NETXX Software Documentation.

Naturally, any external message processor or preprocessor that generates new outgoing network messages must put them into a P*.NET file so that network1 can find it and process it.