Ulrich Bogensperger

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6 years ago.

How to implement a socket server properly?

Hello,

I am trying to build a simple socket server using TCPSocket, but my program crashes at some point. What I do is:

    init_server_socket( &server_socket, server_port );

    // listen on server socket; handle up to MAX_CLIENTS connections
    server_socket.listen( MAX_CLIENTS );

    for(;;) {
        printf( "Waiting for connection on port %d...\n", server_port );
        client = server_socket.accept( &error );

        printf( "Got connection, waiting for data...\n" );

        n = client->recvfrom( &client_adr, buf, sizeof(buf) );

        if( n < 0 ) {
            printf( "Error %d while receiveing from socket\n", n );
        }
        else {
            printf( "Received %d chars from %s\n", n, client_adr.get_ip_address() );
            client->send( ">", 1 );
            client->send( buf, n );
        }

        // need to close the client socket to free resources allocated by socket.accept()
        printf( "Closing client socket...\n" );
        client->close();                                                  <--- crash here
        printf( "--- socket closed ---\n\n" );
    }

The program receives a message and sends it back, that is OK. Then it crashes at client->close() with a stack overflow. 

++ MbedOS Error Info ++
Error Status: 0x80020125 Code: 293 Module: 2
Error Message: CMSIS-RTOS error: Stack overflow
Location: 0x800F349
File:mbed_rtx_handler>+62
Error Value: 0x1
Current Thread: Id: 0x2000D464 Entry: 0x800F267 StackSize: 0x800F852 StackMem: 0x800F847 SP: 0x2004FF20
For more info, visit: https://armmbed.github.io/mbedos-error/?error=0x80020125
-- MbedOS Error Info --

The documentation says, that the client socket has to be closed after usage, but this does not seem to work... What am I doing wrong?

My platform is the STM disco_f746ng. I am compiling locally using the ARM-GCC.

Many thanks in advance.

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