给出在windows下用C语言实现客户端和服务端进行udp通信的示例代码

以下是在Windows下用C语言实现UDP通信的示例代码：

服务端代码：

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

#pragma comment(lib, "ws2_32.lib")

int main()
{
    WSADATA wsaData;
    SOCKET serverSocket;
    SOCKADDR_IN serverAddr, clientAddr;
    int clientAddrLen = sizeof(clientAddr);
    char buffer[1024];
    int recvLen;

    // 初始化Winsock
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
    {
        printf("WSAStartup failed.\n");
        return 1;
    }

    // 创建socket
    serverSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (serverSocket == INVALID_SOCKET)
    {
        printf("Socket creation failed.\n");
        WSACleanup();
        return 1;
    }

    // 绑定地址和端口
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    serverAddr.sin_port = htons(12345);
    if (bind(serverSocket, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR)
    {
        printf("Bind failed.\n");
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    printf("Server is listening on port 12345...\n");

    // 接收数据
    while (1)
    {
        recvLen = recvfrom(serverSocket, buffer, sizeof(buffer), 0, (SOCKADDR*)&clientAddr, &clientAddrLen);
        if (recvLen == SOCKET_ERROR)
        {
            printf("Receive failed.\n");
            break;
        }

        printf("Received message from %s:%d\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));
        buffer[recvLen] = '\0';
        printf("Message content: %s\n", buffer);

        // 回复客户端
        if (sendto(serverSocket, buffer, recvLen, 0, (SOCKADDR*)&clientAddr, sizeof(clientAddr)) == SOCKET_ERROR)
        {
            printf("Send failed.\n");
            break;
        }
    }

    // 关闭socket和Winsock
    closesocket(serverSocket);
    WSACleanup();

    return 0;
}

客户端代码：

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

#pragma comment(lib, "ws2_32.lib")

int main()
{
    WSADATA wsaData;
    SOCKET clientSocket;
    SOCKADDR_IN serverAddr;
    char buffer[1024];
    int recvLen;

    // 初始化Winsock
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
    {
        printf("WSAStartup failed.\n");
        return 1;
    }

    // 创建socket
    clientSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (clientSocket == INVALID_SOCKET)
    {
        printf("Socket creation failed.\n");
        WSACleanup();
        return 1;
    }

    // 设置服务端地址和端口
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serverAddr.sin_port = htons(12345);

    // 发送数据
    strcpy(buffer, "Hello, server!");
    if (sendto(clientSocket, buffer, strlen(buffer), 0, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR)
    {
        printf("Send failed.\n");
        closesocket(clientSocket);
        WSACleanup();
        return 1;
    }

    printf("Sent message: %s\n", buffer);

    // 接收回复
    recvLen = recvfrom(clientSocket, buffer, sizeof(buffer), 0, NULL, NULL);
    if (recvLen == SOCKET_ERROR)
    {
        printf("Receive failed.\n");
        closesocket(clientSocket);
        WSACleanup();
        return 1;
    }

    buffer[recvLen] = '\0';
    printf("Received message: %s\n", buffer);

    // 关闭socket和Winsock
    closesocket(clientSocket);
    WSACleanup();

    return 0;
}

其中，服务端监听的端口为12345，客户端连接的地址为127.0.0.1，端口为12345。你可以根据需要修改这些参数。