#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/socket.h>#include <sys/file.h>#include <arpa/inet.h>#include <fnctl.h>#include <signal.h>#define MAX_BUFFER 1024int global_socket; // Global, the socket, used in asynch handlertypedef struct sockaddr SA;void SIGIO_handler( int type ){  struct sockaddr_in address;  unsigned int addr_length;  int size;  char buffer[MAX_BUFFER];  do  {    addr_length = sizeof( address );    size = recvfrom( global_socket, buffer, MAX_BUFFER, 0 , (SA*) &address, &addr_length );    if (size < 0)    {      // Handle errors, but (obviously) just ignore EWOULDBLOCK    }    else    {      // Do something with the data.    }  } while( size >= 0 )}int setup( int port ){  struct sigaction handler;  struct sockaddr_in address;    // Setup socket  int sock = socket( PF_INET, SOCK_DGRAM, IPPROTO_UDP ); // Add error check    memset( &address, 0, sizeof( address ));  address.sin_family = AF_INET;  address.sin_addr.s_addr = htonl( INADDR_ANY );  address.sin_port = htons( port );  bind( sock, (SA*) &address, sizeof( address ) ); // Add error check  // Setup asynchronous handler  handler.sa_handler = SIGIO_handler;  sigfillset(&handler.sa_mask); // Add error check  handler.sa_flags = 0;  // register signal handler  sigaction( SIGIO, &handler, 0 ); // Add error check  // "own" the socket  fcntl( sock, F_SETOWN, getpid() ); // Add error check  // make it non-blocking and asynchronous  fcntl( sock, F_SETFL, O_NONBLOCK | FASYNC ); // Add error check  return sock;}void main(){  global_socket = setup( 4000 );    GameLoop();}