Appendix A. AT Commands
COM/IP software accepts a Hayes-compatible AT command set. Some AT commands are ignored, as they are only relevant to a real modem. Below are the AT commands supported by the COM/IP Redirector.
A - Answer
When an incoming connection is pending, this command will instruct COM/IP to open the connection, and return a CONNECT response string. If there is no pending incoming connection, then the output will be ERROR.
D - Dial Command
This command will instruct COM/IP to establish a connection to the named-host or IP address, following the D command. This works similarly to a modem, except that a network address is specified, instead of a phone number. The T and P (tone or pulse) modifiers are allowed to follow the D command, and they are simply ignored. COM/IP will attempt to connect to the specified host, and return a CONNECT response string on success, or NO CARRIER upon failure.
If the connection fails, then an additional error message beginning with WINSOCK will be output, providing more detail about the failed connection. As with a normal modem, if any key is pressed while the connection attempt is in progress, then the connection will be aborted, and the output will be NO CARRIER.
E0, E1 - Command-Mode Echo
This command will enable or disable character echoing while COM/IP is in command mode (i.e., accepting AT commands). E1 will enable echo, and E0 will disable echo.
The default is E1.
F0, F1 - Online Echo
This command will enable or disable character echoing while COM/IP is in online mode (i.e., actually connected to a remote host). F1 will enable echo, and F0 will disable echo.
The default is F0.
H0 - Go Off-Hook
This command will only be valid when COM/IP has established a connection, and it will cause the current connection to close.
O - Return to Online Mode
This command will only be valid when COM/IP has established a connection. It will cause COM/IP to exit command mode, and return control of the serial line to the current Telnet connection.
Sr=n - Write to an S-Register
This command will write a value "n" into the S-register numbered "r". The S-registers supported are listed in Appendix B. Standard S-Registers and Appendix C. COM/IP S-Registers. If the query refers to an unsupported S-register, then the output will be ERROR, and parsing of the current command line will be terminated.
Sr? - Query an S-Register
V0, V1 - Verbose
This command will set COM/IP to use text or numeric responses. V0 will enable numeric responses (e.g., 0 is the equivalent of OK), and V1 will enable text responses (e.g., OK, NO CARRIER, etc.).
The default is V1.
W0, W1, W2 - Negotiation Progress Messages
In addition to the CONNECT response string, this command may be used to enable the CARRIER, PROTOCOL and COMPRESSION messages that are available with some modems. W0 and W2 will disable the extended progress messages, and W1 will enable the CARRIER and PROTOCOL messages, which will always be reported as NONE.
Any value other than zero in S95 will override this setting. The default is W0.
Z - Reset
This command will reset COM/IP to default settings, and close any currently open connection.
&C0, &C1, &C2 - Data Carrier Detect Options
This command will control how the Data Carrier Detect (DCD) line will be reported by COM/IP. &C0 will cause COM/IP to always report the DCD line as ON.
&C1 will cause COM/IP to report the DCD line as OFF while there is no connection. It will be switched to ON immediately after the CONNECT message, and to OFF again when the connection is lost. This is the default setting.
&C2 will cause COM/IP to report the DCD line as ON while there is no connection. It will be switched to OFF while a connection is being established, and to ON again once the connection is made.
&D0, &D1, &D2, &D3 - Data Terminal Ready Options
This command will control how the Data Terminal Ready (DTR) line will be interpreted by COM/IP.
&D0 will cause COM/IP to ignore the DTR line. This is the default setting.
&D1 will cause an ON-to-OFF transition of the DTR line to simply put COM/IP in command mode, while maintaining the currently open connection.
&D2 or &D3 will cause an ON-to-OFF transition of the DTR line to close any currently open connections. It will issue a NO CARRIER response if one was open, and put COM/IP in command mode.
&F, &F1 - Set to Factory Defaults
This command is the same as the ATZ command.
&S0, &S1, &S2 - Data Set Ready Options
This command will control how the Data Set Ready (DSR) line will be reported by COM/IP.
&S0 will cause COM/IP to always report the DSR line as ON. This is the default setting.
&S1 will cause COM/IP to report the DSR line as OFF while there is no connection opened. It will switch to ON when attempting to open a connection, and then to OFF again once the connection is closed.
&S2 will cause COM/IP to report the DSR line as OFF while there is no connection opened. It will switch to ON when a connection is opened, and then to OFF again once the connection is closed.
&V - View current settings
This command will display the current settings that are being used by COM/IP. A sample output using the default settings is shown below:
E1 F1 W0 &C1 &D0 &S0
S0:000 S02:043 S03:013 S04:010 S05:008 S12:050 S95:000
S1001:002 S1002:000 S1003:001 S1004:001 S1005:003
S1006:000 S1007:243 S1008:023