TCP client-server SIGPIPE

Question

I am designing and testing a client server program based on TCP sockets(Internet domain). Currently , I am testing it on my local machine and not able to understand the foll

Answer 1

SIGPIPE is raised because you are attempting to write to a socket that has been closed. This does indicate a probable bug so check your application as to why it is occurring and attempt to fix that first.

Attempting to just mask SIGPIPE is not a good idea because you don't really know where the signal is coming from and you may mask other sources of this error. In multi-threaded environments, signals are a horrible solution.

In the rare cases were you cannot avoid this, you can mask the signal on send. If you set the MSG_NOSIGNAL flag on send()/sendto(), it will prevent SIGPIPE being raised. If you do trigger this error, send() returns -1 and errno will be set to EPIPE. Clean and easy. See man send for details.

Answer 2

SIGPIPE is sent when you try to write to an unconnected pipe/socket. Installing a handler for the signal will make send() return an error instead.

signal(SIGPIPE, SIG_IGN);

Alternatively, you can disable SIGPIPE for a socket:

int n = 1;
setsockopt(thesocket, SOL_SOCKET, SO_NOSIGPIPE, &n, sizeof(n));

Also, the data amounts you're mentioning are not very high. Likely there's a bug somewhere that causes your connection to close unexpectedly, giving a SIGPIPE.