portable_udp.cpp

#ifdef _WIN32
// taken from https://stackoverflow.com/questions/28027937/cross-platform-sockets
/* See http://stackoverflow.com/questions/12765743/getaddrinfo-on-win32 */
#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0501  /* Windows XP. */
#endif
#include <winsock2.h>
#include <ws2tcpip.h>
#pragma comment(lib,"ws2_32.lib") //Winsock Library
#else
/* Assume that any non-Windows platform uses POSIX-style sockets instead. */
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>  /* Needed for getaddrinfo() and freeaddrinfo() */
#include <unistd.h> /* Needed for close() */
typedef int SOCKET;
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>


#define PORT 9034

int sockInit(void)
{
#ifdef _WIN32
    WSADATA wsa_data;
    return WSAStartup(MAKEWORD(1, 1), &wsa_data);
#else
    return 0;
#endif
}

int sockQuit(void)
{
#ifdef _WIN32
    return WSACleanup();
#else
    return 0;
#endif
}

/* Note: For POSIX, typedef SOCKET as an int. */
int sockClose(SOCKET sock)
{
    int status = 0;
#ifdef _WIN32
    status = shutdown(sock, SD_BOTH);
    if (status == 0) { status = closesocket(sock); }
#else
    status = shutdown(sock, SHUT_RDWR);
    if (status == 0) { status = close(sock); }
#endif
    return status;
}

int main(void)
{
    fd_set master;    // master file descriptor list
    SOCKET listener;     // listening socket descriptor

    char buf[256];    // buffer for client data
    int nbytes;

    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(PORT);
    
    struct sockaddr_in sender;


    sockInit();
    listener = socket(AF_INET, SOCK_DGRAM, 0);
    if (listener == INVALID_SOCKET || listener < 0) {
        exit(1);
    }

    //fixme: check error values for unix
    if (bind(listener, (struct sockaddr*)&server, sizeof(server)) == SOCKET_ERROR) {
        sockClose(listener);
        exit(2);
    }

    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 10000; // 10ms
    int n;
    int senderSize = sizeof(sender);

    // main loop
    for (;;) {
        FD_ZERO(&master);    // clear the master and temp sets
        // add the listener to the master set
        FD_SET(listener, &master);

        n = select(listener, &master, NULL, NULL, &tv);

        if (n > 0) {
            // leer el socket
            nbytes = recvfrom(listener, buf, sizeof(buf), 0, (sockaddr*)&sender , &senderSize);
            if (nbytes > 0) {
                // hacer algo...
            }
        }
        else if (n < 0) {
            perror("select");
            exit(4);
        }

        //hacer otra cosa...
    }

    sockQuit();

    return 0;
}