CODEWITHSUNDEEP
c++socketspipempipetsc
wvn
wvn

Reputation: 675

Can I write to a closed socket and forcefully correct the broken pipe error?

I have an application that runs on a large number of processors. On processor 0, I have a function that writes data to a socket if it is open. This function runs in a loop in a separate thread on processor 0, i.e. processor 0 is responsible for its own workload and has an extra thread running the communication on the socket.

//This function runs on a loop, called every 1.5 seconds
void T_main_loop(const int& client_socket_id, bool* exit_flag)
{
    //Check that socket still connected.
    int error_code;
    socklen_t error_code_size = sizeof(error_code);
    getsockopt(client_socket_id, SOL_SOCKET, SO_ERROR, &error_code, &error_code_size);

    if (error_code == 0)
    {
        //send some data
        int valsend = send(client_socket_id , data , size_of_data , 0);
    }
    else
    {
        *(exit_flag) = false; //This is used for some external logic.
        //Can I fix the broklen pipe here somehow?
    }
}

When the client socket is closed, the program should just ignore the error, and this is standard behavior as far as I am aware.

However, I am using an external library (PETSc) that is somehow detecting the broken pipe error and closing the entire parallel (MPI) environment:

[0]PETSC ERROR: Caught signal number 13 Broken Pipe: Likely while reading or writing to a socket

I would like to leave the configuration of this library completely untouched if at all possible. Open to any robust workarounds that are possible.

Upvotes: 1

Views: 699

Answers (1)

Maxim Egorushkin
Maxim Egorushkin

Reputation: 136425

By default, the OS sends the thread SIGPIPE if it tries to write into a (half) closed pipe or socket.

One option to disable the signal is to do signal(SIGPIPE, SIG_IGN);.

Another option is to use MSG_NOSIGNAL flag for send, e.g. send(..., MSG_NOSIGNAL);.

Upvotes: 2

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