The Synchronet Terminal Server is responsible for providing that “old school” BBS user interface over dial-up modems and classic Internet console protocols (e.g. Telnet).

• Supports ANSI X3.64 (color and monochrome), PETSCII, RIP, and dumb terminals
• Supports US-ASCII, CP437 (a.k.a. IBM Extended ASCII), UTF-8 (UNICODE), and CBM/PETSCII character sets
• Supported Protocols: Telnet, RLogin, SSH, and raw TCP

The Synchronet Terminal Server can be configured via SCFG:Servers->Terminal Server:

╔═══════════════════════════════════════════╗
║              Terminal Server              ║
╠═══════════════════════════════════════════╣
║ │Enabled                       Yes        ║
║ │Log Level                     Info       ║
║ │Serving Nodes                 1-4        ║
║ │SSH Support...                Port 22    ║
║ │Telnet Support...             Port 23    ║
║ │RLogin Support...             Port 513   ║
║ │40 Column PETSCII Support     Port 64    ║
║ │80 Column PETSCII Support     Port 128   ║
║ │DOS Program Support           Yes        ║
║ │Max Concurrent Connections    Unlimited  ║
║ │Max Login Inactivity          10 minutes ║
║ │Max New User Inactivity       1 hour     ║
║ │Max User Inactivity           10 minutes ║
║ │Output Buffer Drain Timeout   10 ms      ║
║ │Execute Timed Events          Yes        ║
║ │Execute QWK-related Events    Yes        ║
║ │Lookup Client Hostname        Yes        ║
║ │JavaScript Settings...                   ║
║ │Failed Login Attempts...                 ║
╚═══════════════════════════════════════════╝

... or configured (on Windows) via SBBSCTRL:Telnet->Configure dialog

... or configured by manually editing the [BBS] section of the ctrl/sbbs.ini file

These control-key combinations have special purpose at almost any-time while using the Terminal Server:

Global control-keys are handled in sbbs_t::handle_ctrlkey(), called from sbbs_t::inkey() in inkey.cpp and exposed in JavaScript via console.inkey().

Global control key handling may be disabled/re-enabled (per key) programmatically via the JavaScript console.ctrlkey_passthru property:

js.on_exit("console.ctrlkey_passthru = " + console.ctrlkey_passthru);
console.ctrlkey_passthru|=(1<<16);      // Disable Ctrl-P handling in sbbs

Custom global control-key handlers may be installed via SCFG->External Programs->Global Hot Key Events:

╔═══════════════════════════════════════════╗
║           Global Hot Key Events           ║
╠═══════════════════════════════════════════╣
║ │Ctrl-P    ?privatemsg.js                 ║
║ │Ctrl-U    ?nodelist.js -active           ║
║ │                                         ║
╚═══════════════════════════════════════════╝

Additional control-key combinations have special behavior during line (text string) input:

The line/string input control-keys are handled via sbbs_t::getstr() in getstr.cpp and exposed in JavaScript via console.getstr().

The Synchronet Terminal Server endeavors to support most extended-keys (e.g. home, end, arrow-keys, etc.) on most terminals while simultaneously supporting control-key equivalents for all terminals.

Telnet clients (a.k.a. terminal programs) are supported, by default, on the standard Telnet TCP port: 23.

The Synchronet Terminal Server will negotiate Telnet options with the client (enforcing echo and non-line-at-a-time modes), perform IAC (character 255) escaping, and CR/LF->CR and CR/NUL->CR translation (when not in binary mode).

Telnet support in the Synchronet Terminal Server can be configured via SCFG:Servers->Terminal Server->Telnet Support:

╔══════════════════════════════════╗
║          Telnet Support          ║
╠══════════════════════════════════╣
║ │Enabled             Yes         ║
║ │Interfaces          0.0.0.0, :: ║
║ │Port                23          ║
║ │Command Debug       No          ║
║ │Send Go-Aheads      Yes         ║
╚══════════════════════════════════╝

Telnet options are negotiated between the client and server, normally without any indication to the user.

If no Telnet options are received by the Terminal Server during an initial client session on the configured Telnet port, the Terminal Server will revert the client to just “Raw TCP” protocol.

Telnet options can be re-negotiated at any time during a Telnet session, but most options are only negotiated during the initial connection.

The BINARY_TX option (disabling special treatment of CR/LF and CR/NUL) is dynamically negotiated as needed, for file transfers.

The Terminal server logs all Telnet option negotiations using a Debugging log-level:

  6/20  05:56:41p  Node 1 sending telnet cmd: WILL Echo
  6/20  05:56:41p  Node 1 sending telnet cmd: WILL Suppress Go Ahead
  6/20  05:56:41p  Node 1 sending telnet cmd: DO Terminal Type
  6/20  05:56:41p  Node 1 sending telnet cmd: DO Terminal Speed
  6/20  05:56:41p  Node 1 sending telnet cmd: DO Send Location
  6/20  05:56:41p  Node 1 sending telnet cmd: DO Negotiate About Window Size
  6/20  05:56:41p  Node 1 sending telnet cmd: DO New Environment Option
  6/20  05:56:41p  Node 1 received telnet cmd: DO Echo
  6/20  05:56:41p  Node 1 received telnet cmd: DO Suppress Go Ahead
  6/20  05:56:41p  Node 1 received telnet cmd: WILL Terminal Type
  6/20  05:56:41p  Node 1 requesting telnet terminal type
  6/20  05:56:41p  Node 1 received telnet cmd: WON'T Terminal Speed
  6/20  05:56:41p  Node 1 sending telnet cmd: DON'T Terminal Speed
  6/20  05:56:41p  Node 1 received telnet cmd: WON'T Send Location
  6/20  05:56:41p  Node 1 sending telnet cmd: DON'T Send Location
  6/20  05:56:41p  Node 1 received telnet cmd: WILL Negotiate About Window Size
  6/20  05:56:41p  Node 1 received telnet sub-negotiation command: Negotiate About Window Size
  6/20  05:56:41p  Node 1 received telnet window size: 80x24
  6/20  05:56:41p  Node 1 received telnet cmd: WON'T New Environment Option
  6/20  05:56:41p  Node 1 received telnet sub-negotiation command: Terminal Type
  6/20  05:56:41p  Node 1 received telnet terminal type: ANSI

Secure Shell version 2 clients are supported, by default, on the standard SSH TCP port: 22.

SSHv2 support provided by cryptlib.

SSH support in the Synchronet Terminal Server can be configured via SCFG:Servers->Terminal Server->SSH Support:

╔════════════════════════════════════════════╗
║                 SSH Support                ║
╠════════════════════════════════════════════╣
║ │Enabled                       Yes         ║
║ │Interfaces                    0.0.0.0, :: ║
║ │Port                          22          ║
║ │Connect Timeout               10 seconds  ║
║ │Error Level                   Warning     ║
║ │File Transfer (SFTP) Support  No          ║
║ │Max SFTP Inactivity           N/A         ║
╚════════════════════════════════════════════╝

The SSH private key is stored in the file ctrl/cryptlib.key and is encrypted with the configured System Password (from SCFG->System). If the System Password is changed after the cryptlib.key file has been generated (and encrypted), you will need to delete the key file and recycle the terminal server for the key file to be regenerated and re-encrypted with the new System Password.

The following Terminal Server log message indicates a problem decrypting the cryptlib.key file:

'Couldn't import the session key used to protect the private key' (-22) getting private key

BSD Rlogin (RFC-1282) clients are supported, by default, on the standard RLogin TCP port: 513.

RLogin support in the Synchronet Terminal Server can be configured via SCFG:Servers->Terminal Server->RLogin Support:

╔════════════════════════════════════════════╗
║                RLogin Support              ║
╠════════════════════════════════════════════╣
║ │Enabled                       Yes         ║
║ │Interfaces                    0.0.0.0, :: ║
║ │Port                          513         ║
╚════════════════════════════════════════════╝

Synchronet's RLogin support has gone through some significant changes since its introduction in 2000.

• digital man added initial support for accepting connections from BSD RLogin:

The Synchronet Telnet Server (later referred to as the “Terminal Server”) was enhanced to recognize the BSD RLogin connect sequence on a secondary port (TCP port 513 by default) and bypass the “Login:” prompt if the username specified in either first (client-user-name) or second (server-user-name) strings sent from the RLogin client were recognized as a valid user/login ID (alias). The default behavior was to compare the first (client-user-name) string as the attempted login ID but this could be changed by checking the SBBSCTRL:Telnet->Configure->RLogin->Use 2nd Login Name checkbox. Comparing *both* RLogin-client provided strings was not supported (only one or the other would be compared against the user database).

• The password prompt was still displayed and a valid password required in order to login as the identified user ID. If the user ID was not recognized as a valid user, then the new user application process was started (with the user's alias automatically filled in with the specified client-user-name or server-user-name value).

• digital man added the r2 option to sbbs (console) to use the second RLogin string as the username.
• digital man added support for the Telnet gateway module to be optionally used as a gateway to an RLogin server (e.g. TradeWars Game Server, aka TWGS) - by specifying the TG_RLOGIN mode flag to the telnet_gate function (via Baja or JavaScript). The current user's login ID (alias) was sent as the client-user-name string and the user's real name was sent as the server-user-name string as part of the outbound RLogin connection establishment.

• Deuce changed the default RLogin configuration (by this time stored in the Options field of the [bbs] section of the sbbs.ini file to use the second string sent by the RLogin client as the login ID (USE_2ND_RLOGIN).
• Deuce changed the default configuration to enable/accept RLogin connections.
• Deuce added support for automatic-login if a valid user password was supplied in either the client-user-name or server-user-name strings sent from the RLogin client (which string was assumed to be the user ID and which was assumed to be the password was determined by the “Use 2nd Login Name” option) or the client's IP address was listed in the (newly introduced) text/rlogin.can file, then the user would be automatically logged in without needing to provide/send a password.

• Deuce changed the RLogin connection behavior as follows:

if (specified user does not exist) {
    if (rlogin password recieved) {
        create new user with specified password
    }
    else {
        create new user with random password
        show password to user
        allow user to change password
        validate new password
   }
}
else {
    if(password is correct) {
        logon user
    }
    else {
        prompt for current password
    }
}

• echicken added a new mode flag (TG_SENDPASS) to the telnet_gate function which if combined with TG_RLOGIN mode flag would send the current user's password as the second RLogin string (server-user-name) during an outbound RLogin connection (instead of the default behavior of sending the current user's real name).

• mcmlxxix removed echicken's TG_SENDPASS mode flag support and created a new function (bbs.rlogin_gate) which accepted arguments to be sent to the remote RLogin server (presumably, the user's name and password, in that order).

• digital man removed and deprecated the USE_2ND_RLOGIN option (and related sbbs command-line option and sbbsctrl checkbox) as this is now the only behavior supported by the Synchronet Terminal Server: the first string received from the RLogin client (client-user-name) may be a password, the second string received (server-user-name) must be a valid user ID (alias).
• digital man changed the bbs.rlogin_gate function to accept 3 optional arguments: client-user-name, server-user-name, and terminal, in the order specified by the RFC-1282.

Additional JavaScript objects are available to Terminal Server modules only:

• bbs object
• console object

• Synchronet External Plain Old Telephone System Support (SEXPOTS)
• Servers