Modem Connectivity (from Linux box)

[Pashmina]

Hi,
Using Java and RxTx, I am connecting to some devices (from a Linux box), by dialing to the modem.
I am able to establish to connection, since i get the CONNECT string(CONNECT 9600). After that, i get some garbage characters, and then a NO CARRIER response.
I want to know that why after getting connected to the modem(getting CONNECT), I am get NO CARRIER. Could it be that my modem is not able to recognising the garbage characters that the remote modem is sending or could it be something else?

[Stuart Browne]

It depends what you are connecting too.

Getting 'garbage characters' straight after a connect sounds a bit odd however.

I'd verify you don't have a BAUD rate mismatch (are you sure the other end is supposed to be talking at 9600?) and go from there.

What is the other end supposed to say when you connect?

[Ragu_3]

The garbage characters are in fact the data stream, rest assured that the pppd is coming up. Trying putting in `noauth' instead of `auth' in your /etc/ppp/options file. I think that the peer is trying to authenticate itself and failing miserably!

[Pashmina]

The entry in /etc/pp/options is "noauth" only. There is some communication problem due to which, the connection between both the modems is breaking off...but i don't know how to determine why that is happening

[Jan Sladky]

It can be several things, hard to say the exact reason,(authentication, different bit rates on both sides, protocol definition) can you post your wvdial.conf or what you are using for dialing (kinternet)

first of all I suggest enable the stupid mode:
Stupid Mode = 0

after that the dialer will ingnore prompts from other side

post result

br Jan

[Pashmina]

I am not using wvdial.conf. We are developing an application which dials to devices and gets data from them. So the details like dialing command, user id, password are taken from XML files.

[Matti_Kurkela]

When modem says "CONNECT", it has established the connection and anything after that should come from the remote computer. If there are no error correction methods in use between the modems, the garbage characters might be caused by bad telephone line quality.

Is this supposed to be a PPP connection, a terminal connection or a raw data transfer between two programs over the modem link?

For troubleshooting a PPP connection, increase the logging level of pppd. If it's a terminal connection, try using minicom or some other full-featured terminal emulator.

Some modems can display the reason why the latest connection failed and/or the quality parameters for that connection. The command to do this is specific to the model of the modem, but on some modems based on the very common Rockwell/Conexant chips it might be "AT&V1".

Try to check the lower levels of functionality before moving on to the higher levels. I'd first try to find out if the modem is breaking the connection because the phone line quality is bad, since the connection between your computer and your modem obviously works. After that, you need the help of the administrator of the remote computer: seeing how the situation looks at his/her end vs. your end may reveal some vital clues.

From your later posts in this thread, I understood you're developing your own software. You should ask the administrator of the remote computer to find out if the logs at his/her end tell anything about why the connection was closed. It may be that the server terminated the connection because your software did not give a "correct" answer to the server.

[Bojan Nemec]

Hi,

I supose you are doing a raw data connection or a terminal connection.

If so I sugest that you first try to connect to the device using minicom, so you can test the baud rate etc...
When this works, transfer the settings in your application.
What abbout character size? 16 bit (Used by Java) and 8 or 7 bit used by modems?

Bojan