Receive data with UDP socket in VS2013

Question

I wanted to receive an *.xml data by port 3702 .

So I made a example Server. And sended data by three port 1500,2500,3702 .(Edit the PORT in line 43)

It worked and printed data correctly from port 1500,2500. But when I set the PORT to 3702.

it returned me a error: **Bind failed with error code :10048**

I found that maybe it existed other Client IP were sending data by PORT 3702 in my LAN. How can I fix it?

#include<stdio.h>
#include<winsock2.h>

#pragma comment(lib,"ws2_32.lib") //Winsock Library

#define BUFLEN 8192  //Max length of buffer
#define PORT 3702   //The port on which to listen for incoming data

int main()
{
    SOCKET s;
    struct sockaddr_in server, si_other;
    int slen, recv_len;
    char buf[BUFLEN];
    WSADATA wsa;

    slen = sizeof(si_other);

    //Initialise winsock
    printf("\nInitialising Winsock...");
    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
    {
        printf("Failed. Error Code : %d", WSAGetLastError());
        exit(EXIT_FAILURE);
    }
    printf("Initialised.\n");

    //Create a socket
    if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == INVALID_SOCKET)
    {
        printf("Could not create socket : %d", WSAGetLastError());
    }
    printf("Socket created.\n");

    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(PORT);

    //Bind
    if (bind(s, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
    {
        printf("Bind failed with error code : %d", WSAGetLastError());
        exit(EXIT_FAILURE);
    }
    puts("Bind done");

    //keep listening for data
    while (1)
    {
        printf("Waiting for data...");
        fflush(stdout);

        //clear the buffer by filling null, it might have previously received data
        memset(buf, '\0', BUFLEN);

        //try to receive some data, this is a blocking call
        if ((recv_len = recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *) &si_other, &slen)) ==     SOCKET_ERROR)
        {
            printf("recvfrom() failed with error code : %d", WSAGetLastError());
            //exit(EXIT_FAILURE);
        }

        //print details of the client/peer and the data received
        printf("Received packet from %s:%d\n", inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port));
        printf("Data: %s\n", buf);

        //now reply the client with the same data

    }

    closesocket(s);
    WSACleanup();
    return 0;
}

Answer 1

This is due to Address already in use .

Typically, only one usage of each socket address (protocol/IP address/port) is permitted. This error occurs if an application attempts to bind a socket to an IP address/port that has already been used for an existing socket, or a socket that was not closed properly, or one that is still in the process of closing. For server applications that need to bind multiple sockets to the same port number, consider using setsockopt ( SO_REUSEADDR ).

Client applications usually need not call bind at all - connect chooses an unused port automatically. When bind is called with a wildcard address (involving ADDR_ANY ), a WSAEADDRINUSE error could be delayed until the specific address is committed. This could happen with a call to another function later, including connect , listen , WSAConnect , or WSAJoinLeaf .