socket编程UDP小例子

注：代码在VS2015测试正常
服务器代码如下：

#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main(void)
{
    WSADATA wsaData = { 0 };   //套接字信息结构
    SOCKET ServerSocket = INVALID_SOCKET;  //服务端套接字
    SOCKADDR_IN ServerAddr = { 0 };
    SOCKADDR_IN ClientAddr = { 0 };
    int iClientAddr = sizeof(ClientAddr);
    USHORT usPort = 18000;  //服务器端口
    //初始化
    if (WSAStartup(MAKEWORD(2,2),&wsaData))
    {
        printf("WSAStartup failed with error code: %d\n",WSAGetLastError());
        return -1;
    }
    //判断版本
    if (LOBYTE(wsaData.wVersion)!=2||HIBYTE(wsaData.wVersion)!=2)
    {
        printf("wVersion not 2.2\n");
        return -2;
    }
    //创建服务器套接字
    ServerSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (SOCKET_ERROR == ServerSocket)
    {
        printf("socket failed with error code: %d\n", WSAGetLastError());
        return -3;
    }
    //设置服务器地址
    ServerAddr.sin_family = AF_INET;
    ServerAddr.sin_port = htons(usPort);
    ServerAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
    //绑定服务器地址
    if (SOCKET_ERROR == bind(ServerSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr)))
    {
        printf("bind failed with error code: %d\n", WSAGetLastError());
        closesocket(ServerSocket);
        WSACleanup();
        return -4;
    }
    printf("bind successfully......\n");
    printf("ready recv message......\n");
    char buffer[1024] = { 0 };
    int iRecv = 0;
    int iSend = 0;
    while (1)
    {
        memset(buffer, 0, sizeof(buffer));
        //接收数据
        iRecv = recvfrom(ServerSocket, buffer, sizeof(buffer), 0, (SOCKADDR*)&ClientAddr, &iClientAddr);
        if (iRecv == SOCKET_ERROR)
        {
            printf("recvfrom failed with error code: %d\n", WSAGetLastError());
            closesocket(ServerSocket);
            WSACleanup();
            return -7;
        }
        printf("recvfrom client message:%s\n", buffer);
        memset(buffer, 0, sizeof(buffer));
        printf("Input message:");
        gets_s(buffer);
        //发送数据
        iSend = sendto(ServerSocket, buffer, strlen(buffer), 0, (SOCKADDR*)&ClientAddr, iClientAddr);
        if (iSend == SOCKET_ERROR)
        {
            printf("sendto failed with error code: %d\n", WSAGetLastError());
            closesocket(ServerSocket);
            WSACleanup();
            return -7;
        }
    }
    //关闭，清理
    closesocket(ServerSocket);
    WSACleanup();
    return 0;
}

客户端代码如下：

#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main(void)
{
    WSADATA wsaData = { 0 }; //套接字信息结构
    SOCKET ClientSocket = INVALID_SOCKET;  //客户端套接字
    SOCKADDR_IN ServerAddr = { 0 };        //服务端地址
    SOCKADDR_IN ClientAddr = { 0 };        //客户端地址 
    int iClientAddr = sizeof(ClientAddr);              
    int iServerAddrSize = sizeof(ServerAddr);
    USHORT usPort = 18000;   //服务器端口
    //初始化
    if (WSAStartup(MAKEWORD(2, 2), &wsaData))
    {
        printf("WSAStartup failed with error code: %d\n", WSAGetLastError());
        return -1;
    }
    //判断版本
    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)
    {
        printf("wVersion not 2.2\n");
        return -2;
    }
    //创建客户端UDP套接字
    ClientSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (SOCKET_ERROR == ClientSocket)
    {
        printf("socket failed with error code: %d\n", WSAGetLastError());
        return -3;
    }
    //设置服务器地址
    ServerAddr.sin_family = AF_INET;
    ServerAddr.sin_port = htons(usPort);
    ServerAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");

    printf("ready send message......\n");
    char buffer[1024] = { 0 }; //数据缓冲区
    int iSend = 0;
    int iRecv = 0;
    while (1)
    {
        memset(buffer, 0, sizeof(buffer));
        printf("Input message:");
        gets_s(buffer);
        //发送数据
        iSend = sendto(ClientSocket, buffer, strlen(buffer), 0,
            (SOCKADDR*)&ServerAddr, iServerAddrSize);
        if (iSend == SOCKET_ERROR)
        {
            printf("send failed with error code: %d\n", WSAGetLastError());
            closesocket(ClientSocket);
            WSACleanup();
            return -7;
        }
        memset(buffer, 0, sizeof(buffer));
        //接收数据
        iRecv = recvfrom(ClientSocket, buffer, sizeof(buffer), 0, (SOCKADDR*)&ClientAddr, &iClientAddr);
        if (iRecv == SOCKET_ERROR)
        {
            printf("recvfrom failed with error code: %d\n", WSAGetLastError());
            closesocket(ClientSocket);
            WSACleanup();
            return -7;
        }
        printf("recvfrom server message: %s\n", buffer);
    }
    //关闭，清理
    closesocket(ClientSocket);
    WSACleanup();
    return 0;
}

如图：