• State Not Answered
  • Locked Locked
  • Replies 3 replies
  • Subscribers 22 subscribers
  • Views 1299 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

TCPnet PPP and GPRS trouble

Eric Severson

Hello,

I am struggling to get TCPnet's PPP to work reliably with my GPRS modem.

In low traffic situations everything seems fine -- I am able to get the modem online, open sockets, accept incoming sockets, exchange data, etc. However, when I add on my SSL application, things die during the SSL negotiation. By enabling the PPP debug output I can see that packets are being sent out the PPP interface, but that packets stop coming back in before the negotiation is completed. Eventually the TCP Socket hits its maximum number of retries and fails out.

Now, the interesting thing is that if I try to do the exact same thing through the Ethernet interface (swapping out GPRS/PPP for Ethernet) everything works great.

The only errors I see coming out of the PPP debug are as follows:

On initialization:
"PPP ERR: LCP Magic Number Option Rejected."

Occasionally, during the failed SSL negotiation:
"PPP: *** Processing PPP frame ***
PPP ERR: Frame FCS Check Failed"

I am suspicious that this might be an issue with the time out and retry settings of the PPP and TCP socket interface. Could anybody who has used this with a GPRS/GSM modem give me some pointers?

Any thoughts you might have would be greatly appreciated! Thanks.

  • 0

    I have a little experience of this.

    www.freesoft.org/.../34.htm

    has a good explaination. This is LCP ( a part of the PPP) protocol not being happy with the configuration options you are sending it when you are trying to establish a connnection.

    The magic number is sent by you as a proof that this is not a loopback connection. It prevents false connections. Somewhere in your config it doesn't match what the other end wants.

    It sounds as if you have the option configured and the other end by default expects it not to be on.

    Cheers,

    Dirk

  • 0 in reply to Dirk Veramaak

    Thanks, Dirk. That link is very useful. Do you happen to have any insight as to how I can configure that Magic Number option in TCPnet? I don't have the source code, so all of my configuration is done through the Net_Config.c file -- and I am not seeing any obvious ways to manipulate/disable the Magic Number.

    Also, I have been able to get my SSL to work over PPP. It turned out that I my debug code (which was quiet extensive) was loading down the processor too much.

    I am now getting a new error message from TCPnet:
    "TCP ERR: Out of range sequence number received" during my high-traffic SSL negotiation.

    However, everything seems to work ok...

    -Eric

  • 0 in reply to Eric Severson

    Sorry,

    I've never actually used TCPnet at all so don't know the specifics of the config. In any case, if you have PPP working now, that implies that LCP must be good.

    Maybe overloading your procssor meant a funny message got sent to LCP or the other end just got confused due to the delays.

    It may just have been a red herring.

    Cheers,

    Dirk