Question

How to create UDP client server socket communication on windows in C

Answer 1

/*
You need to link the library: libws2_32.a 
OR
-lwsock32
-lws2_32
from c:\TDM-GCC-64\x86_64-w64-mingw32\lib32\
OR
c:\MinGW\lib\
if you using GCC on windows
*/
   
// Client and Server are on the same computer, with different exe files and two console windows 

// UDP Server program

#include <stdio.h>
#include <WinSock2.h>

int main() {
    printf("UDP SERVER\n");

    WSADATA Winsockdata;
    SOCKET UDPServerSocket;
    struct sockaddr_in UDPClientAddr;
    int UDPClientAddrLen = sizeof(UDPClientAddr);
    char Buffer[512];

    // STEP-1 WSAStartUp
    if (WSAStartup(MAKEWORD(2, 2), &Winsockdata) != 0) {
        printf("SERVER: WSAStartUp Failed");
    }
    printf("SERVER: WSAStartUp Success\n");

    // STEP-2 Fill UDPClient Struct
    UDPClientAddr.sin_family = AF_INET;
    UDPClientAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    UDPClientAddr.sin_port = htons(8888);

    //STEP-3 Create Socket
    if ((UDPServerSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == INVALID_SOCKET) {
        printf("SERVER: UDP Server: Create Socket Failed, Error: %d\n", WSAGetLastError());
    }
    printf("SERVER: UDP Server: Create Socket Success\n");

    //STEP-4 bind
    if (bind(UDPServerSocket, (SOCKADDR*)&UDPClientAddr, sizeof(UDPClientAddr)) == SOCKET_ERROR) {
        printf("SERVER: Binding Failed, Error: %d", WSAGetLastError());
    }
    printf("SERVER: Binding Success\n");

    // STEP-5 RecvFrom Message from Client
    if (recvfrom(UDPServerSocket, Buffer, sizeof(Buffer), MSG_PEEK, (SOCKADDR *)&UDPClientAddr, &UDPClientAddrLen) == SOCKET_ERROR) {
        printf("SERVER: Receive Failed, Error: %d\n", WSAGetLastError());
    }
    printf("SERVER: Received Message From Client: %s\n", Buffer);

    // STEP-6 Close Socket
    if (closesocket(UDPServerSocket) == SOCKET_ERROR) {
        printf("SERVER: Close Socket Failed, Error: %d\n", WSAGetLastError());
    }
    printf("SERVER: Close Socket Success\n");

    // STEP-7 Clean
    if (WSACleanup() == SOCKET_ERROR) {
        printf("SERVER: WSACleanup Failed, Error: %d\n", WSAGetLastError());
    }
    printf("SERVER: WSACleanup Success\n");

    return 0;
}




/*
run:

UDP SERVER
SERVER: WSAStartUp Success
SERVER: UDP Server: Create Socket Success
SERVER: Binding Success
SERVER: Received Message From Client: Hello from Client!
SERVER: Close Socket Success
SERVER: WSACleanup Success

*/

// UDP Client program

#include <stdio.h>
#include <WinSock2.h>

int main() {
    printf("UDP CLIENT\n");

    WSADATA WinSockData;

    SOCKET UDPClientSocket;
    struct sockaddr_in UDPServerAddr;
    char Buffer[512] = "Hello from Client!";

    //STEP-1 WSASatrtUp
    if (WSAStartup(MAKEWORD(2, 2),&WinSockData) != 0) {
        printf("CLIENT: WSAStartUp Failed\n");
    }
    printf("CLIENT: WSAStartUp Success\n");

    // STEP-2 Fill UDPServerAddr
    UDPServerAddr.sin_family = AF_INET;
    UDPServerAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    UDPServerAddr.sin_port = htons(8888);

    // STEP-3 Create Socket
    if ((UDPClientSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == INVALID_SOCKET ) {
    //if (iConnect == SOCKET_ERROR) {
       printf("CLIENT: UDP Create Socket Failed, Error: %d\n", WSAGetLastError());
    }
    printf("CLIENT: UDP Create Socket Success\n");

    // STEP-4 Sendto Message to Server
    if (sendto(UDPClientSocket, Buffer, sizeof(Buffer), MSG_DONTROUTE, (SOCKADDR *) &UDPServerAddr, sizeof(UDPServerAddr)) == SOCKET_ERROR) {
        printf("CLIENT: Send Message Failed, Error: %d\n", WSAGetLastError());
    }
    printf("CLIENT: Message Sent!\n");

    // STEP-5 Close Socket
    if (closesocket(UDPClientSocket) == SOCKET_ERROR) {
        printf("CLIENT: Close Socket Failed, Error: %d\n", WSAGetLastError());
    }
    printf("CLIENT: Close Socket Success\n");

    // STEP-6 Clean
    if (WSACleanup() == SOCKET_ERROR){
        printf("CLIENT: WSACleanup Failed, Error: %d\n", WSAGetLastError());
    }
    printf("CLIENT: WSACleanup Success\n");

    return 0;
}




/*
run:

UDP CLIENT
CLIENT: WSAStartUp Success
CLIENT: UDP Create Socket Success
CLIENT: Message Sent!
CLIENT: Close Socket Success
CLIENT: WSACleanup Success

*/

 

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