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Reconnection causes SIGPIPE signal

Posted on 2006-11-21
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Last Modified: 2012-05-05
I have an infinite for loop where a client app is consistently requesting data from a server, using the GNU C socket library.  (It's all happening locally though.  I'm using my localhost as a server, since this is just a test program.)

The basic routine is:

initialize client socket

for (;;) {
     connect to server
     send request
     recv data
}

The data is received fine, and everything works normally when the above is done ONCE.  But if I do this in a loop, I get SIGPIPE signals after two iterations.  This causes the program to terminate.  I can pass MSG_NOSIGNAL to the send() function, but this just generates various broken pipe error messages.  The client continues to receive data normally, but the SIGPIPE messages keep happening.  

I know that a SIGPIPE means that I'm writing to a socket, but nothing is reading from it.  But this doesn't make sense, because the server clearly is reading from it, since I'm successfully getting the data.  Does anyone know what might be happening here?  

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Question by:chsalvia
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4 Comments
 
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Accepted Solution

by:
Kent Olsen earned 1000 total points
ID: 17987098

After the receive, close the connection.

Or test that an active connection doesn't exist before you issue the connect().


Kent
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Expert Comment

by:_iskywalker_
ID: 17987127
yes, dont open too much connections, make the opning connection out from the intereaction
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Assisted Solution

by:avsrivastava
avsrivastava earned 1000 total points
ID: 17987170
One possibility is that the pipe buffer gets full before the client reads any data, which raises the SIGPIPE message.
You anyways read the data correctly because once the client reads the data, the server can read more.

Solution:
Don't send the MSG_NOSIGNAL, catch the SIGPIPE signal.
When you get the message, sleep for a random amount of time(could be predetermined as well).
When the program wakes, try to write again starting from the position where you left(the return value of write tells you till which byte you managed).


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LVL 2

Expert Comment

by:avsrivastava
ID: 17987184
The pipe by default on linux kernel is 64k, so if the data you are writing is only bytes this would not be the problem though.
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