Once a socket is created using the socket() call, it may be set to non-blocking as follows:

    #include "sys/ioctl.h"
    int on =1;
    int off =0;

    //Enable non-blocking
    ioctl (mySocket, FIONBIO, &(on));
    //Disable non-blocking
    ioctl (mySocket, FIONBIO, (char *) &(off));