Monitoring ports

The way you monitor a port is based on its configuration. The main configurations of the ports you monitor are:

• For logging in only (no uucp dial-out) over a directly connected terminal or machine-to-machine link

• For logging in only (no uucp dial-out) over a modem using switched carrier:

  • A modem that does not recognize commands from the DCE and does not send unsolicited characters to the DCE

  • A smart modem. This login mode differs from bi-directional mode in the way the login prompt is written. The prompt is written out immediately when ttymon begins to monitor a port. This can be echoed back by certain devices, such as a smart modem, causing a premature connection indication in the polling ttymon. Because of the prompt mechanism, we recommend that all answering by the modem be turned off. Use the AT commands: ATE0 and ATQ1; see ``Referencing the port'' that describes how to send commands to the modem. Alternatively, use the <Return>/<Linefeed> count with the ttyadm -r flag.

• For logging in only (no uucp dial-out) over a modem using carrier always high:

  • A modem that does not recognize commands from the DCE

  • A smart modem for which you must use the ttyadm -r flag. This ensures that canonical mode with its associated echoing behavior is not set until the modem has successfully connected. Infinite echo is seen when the tty's line discipline and smart modem lock into a loop where they echo characters back and forth to each other. Because of the prompt mechanism described in Step B, adjust the <CR>/<LF> count by +1, the value seen with bidirectional mode, since, in that case, the prompt is not written out immediately. An alternative is for all answering by the modem to be turned off using the following AT commands: ATE0 and ATQ1. Also note that if the -r count is too low, ttymon will change to canonical mode before the modem is connected, resulting in infinite echo because the modem is still in command mode at this point.

• For bidirectional use, using the ttyadm -b flag, for logging in or dialing out over a directly connected terminal or machine to machine link

• For bidirectional use, using the ttyadm -b flag, for logging in or dialing out over a modem using switched carrier:

  • A modem that does not recognize commands from the DCE and does not send unsolicited characters to the DCE

  • A smart modem

• For bidirectional use, using the ttyadm -b flag, for logging in or dialing out over a modem using carrier always high:

  • A modem that does not recognize commands from the DCE

  • A smart modem for which you must use the ttyadm -r flag. This ensures that canonical mode is not set up on the tty before it has successfully connected.