使用Winsocket和C语言，进行SOCKET通讯编程，设计服务端和客户端程序，要求两端能够自由收发讯息

好的，这是一个经典的 Socket 编程问题，我可以为您提供一些基本的思路和代码示例。

首先，服务端和客户端都需要创建一个 Socket 对象，以便进行通信。在 C 语言中，可以使用 Winsock 库来实现 Socket 编程。以下是服务端和客户端的代码示例。

服务端代码示例：

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

int main() {
    // 初始化 Winsock 库
    WSADATA wsaData;
    int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

    // 创建 Socket 对象
    SOCKET listenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (listenSocket == INVALID_SOCKET) {
        printf("Error creating socket: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    // 绑定 Socket 对象到本地地址和端口
    struct sockaddr_in localAddr;
    localAddr.sin_family = AF_INET;
    localAddr.sin_addr.s_addr = INADDR_ANY;
    localAddr.sin_port = htons(12345);
    iResult = bind(listenSocket, (struct sockaddr*) &localAddr, sizeof(localAddr));
    if (iResult == SOCKET_ERROR) {
        printf("Bind failed: %d\n", WSAGetLastError());
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    // 开始监听客户端连接请求
    iResult = listen(listenSocket, SOMAXCONN);
    if (iResult == SOCKET_ERROR) {
        printf("Listen failed: %d\n", WSAGetLastError());
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    // 等待客户端连接
    printf("Waiting for client connection...\n");
    SOCKET clientSocket = accept(listenSocket, NULL, NULL);
    if (clientSocket == INVALID_SOCKET) {
        printf("Accept failed: %d\n", WSAGetLastError());
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    // 接收和发送数据
    char recvBuf[1024];
    char sendBuf[1024];
    while (1) {
        // 接收客户端发来的数据
        iResult = recv(clientSocket, recvBuf, sizeof(recvBuf), 0);
        if (iResult > 0) {
            recvBuf[iResult] = '\0';
            printf("Received: %s\n", recvBuf);

            // 发送数据给客户端
            sprintf(sendBuf, "Hello, %s!", recvBuf);
            iResult = send(clientSocket, sendBuf, strlen(sendBuf), 0);
            if (iResult == SOCKET_ERROR) {
                printf("Send failed: %d\n", WSAGetLastError());
                closesocket(clientSocket);
                WSACleanup();
                return 1;
            }
        } else if (iResult == 0) {
            printf("Connection closed.\n");
            break;
        } else {
            printf("Recv failed: %d\n", WSAGetLastError());
            closesocket(clientSocket);
            WSACleanup();
            return 1;
        }
    }

    // 关闭 Socket 对象
    closesocket(clientSocket);
    closesocket(listenSocket);
    WSACleanup();

    return 0;
}

客户端代码示例：

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

int main() {
    // 初始化 Winsock 库
    WSADATA wsaData;
    int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

    // 创建 Socket 对象
    SOCKET clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (clientSocket == INVALID_SOCKET) {
        printf("Error creating socket: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    // 连接到服务端
    struct sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serverAddr.sin_port = htons(12345);
    iResult = connect(clientSocket, (struct sockaddr*) &serverAddr, sizeof(serverAddr));
    if (iResult == SOCKET_ERROR) {
        printf("Connect failed: %d\n", WSAGetLastError());
        closesocket(clientSocket);
        WSACleanup();
        return 1;
    }

    // 接收和发送数据
    char recvBuf[1024];
    char sendBuf[1024];
    while (1) {
        // 发送数据给服务端
        printf("Enter message: ");
        fgets(sendBuf, sizeof(sendBuf), stdin);
        sendBuf[strlen(sendBuf)-1] = '\0';
        iResult = send(clientSocket, sendBuf, strlen(sendBuf), 0);
        if (iResult == SOCKET_ERROR) {
            printf("Send failed: %d\n", WSAGetLastError());
            closesocket(clientSocket);
            WSACleanup();
            return 1;
        }

        // 接收服务端发来的数据
        iResult = recv(clientSocket, recvBuf, sizeof(recvBuf), 0);
        if (iResult > 0) {
            recvBuf[iResult] = '\0';
            printf("Received: %s\n", recvBuf);
        } else if (iResult == 0) {
            printf("Connection closed.\n");
            break;
        } else {
            printf("Recv failed: %d\n", WSAGetLastError());
            closesocket(clientSocket);
            WSACleanup();
            return 1;
        }
    }

    // 关闭 Socket 对象
    closesocket(clientSocket);
    WSACleanup();

    return 0;
}

以上代码示例只是基本的实现，您可以根据自己的需要进行进一步的修改和扩展。