Hi,

I have a modem that is conencted to serial port of my RedHat Linux machine and I want to listen for RING events on this port. For this, I open the COM port, select the file descriptor and wait for an event to occur. I get the interrupt when I dial my modem, but how can I make sure that select returned because of RING event and not because of some other activity on the serial port?

Thanks,
Ruchika

configure your modem to report events ("RING" , "NO DIALTONE", etc)
X0

Report basic call progress result codes, i.e., OK, CONNECT, RING, NO CARRIER (also, for busy, if enabled, and dial tone not detected), NO ANSWER and ERROR.

X1 Report basic call progress result codes and connections speeds (OK, CONNECT, RING, NO CARRIER (also, for busy, if enabled, and dial tone not detected), NO ANSWER, CONNECT XXXX, and ERROR.
X2 Report basic call progress result codes and connections speeds, i.e., OK, CONNECT, RING, NO CARRIER (also, for busy, if enabled, and dial tone not detected), NO ANSWER, CONNECT XXXX, and ERROR.
X3 Report basic call progress result codes and connection rate, i.e., OK, CONNECT, RING, NO CARRIER, NO ANSWER, CONNECT XXXX, BUSY, and ERROR.
X4 Report all call progress result codes and connection rate, i.e., OK, CONNECT, RING, NO CARRIER, NO ANSWER, CONNECT XXXX, BUSY, NO DIAL TONE and ERROR.

read strings from the modem until the string "RING" is matched

Thanks for the reply AltF4.

After select returns, I now read the RX queue, it cotain "RING" and hence I know that select returned because of RING and handle it.

But now I have another question .. I want to dial into a remote PPP server via a Hayes compatible 1X modem when the device connected to the modem gets a ring interrupt. The modem is connected to the serial port of the Linux box. Heres what I do - I open the COM port, select the port and wait for an event to occur. If I get RING event, I close the COM port and run a script that establishes a PPP connection (runs pppd and chat). Whats happening now is that the I am not able to talk to my modem. The chat script sends AT command to the modem but does not get response from the modem. After a few secs, I see alarm FAILED in /etc/ppp/connect-errors file. I think that somehow the COM port is not getting released and so PPP script is not able to talk to the modem. But I may be wrong. Any clues on what might be happening?

I used minicom to talk to the modem and that works fine. The same chat script used to work until I added the "listen on Ring interrupt" feature before starting the PPP script. Thats why I suspect that the problem has to do with the COM port.

BTW, I am running RedHat Linux 9.0 and am using C++ for port handling and a shell script to establish PPP connection.

Thanks for your help.

try sending a "reset to factory defaults" string (AT&F) or a reset (ATZ) to your modem after you are done waiting for ring