使用Winsock2库实现、创建收发文件的服务器/客服端,实现如下功能：（35分） （1）客户端接受用户输入的传输文件名。 （2）客户端请求服务器端在指定文件夹下传输该文件名所指的文件。 如果指定文件存在，服务器端就将其发送给客户端；反之，则断开连接。

好的，这是一个关于网络编程的问题。我会尽力回答。

首先，使用Winsock2库可以轻松地实现客户端和服务器端之间的通信。下面是一个简单的代码示例，包括客户端和服务器端的代码。

服务器端代码：

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

#define PORT 12345
#define MAX_BUFF_SIZE 1024

int main()
{
    WSADATA wsaData;
    SOCKET serverSocket, clientSocket;
    SOCKADDR_IN serverAddress, clientAddress;
    char buffer[MAX_BUFF_SIZE];
    int bufferLength = 0;
    int clientAddressLength = sizeof(clientAddress);

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

    // 创建服务器端socket
    if ((serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
    {
        printf("Create server socket failed!\n");
        WSACleanup();
        return 1;
    }

    // 设置服务器端地址
    ZeroMemory(&serverAddress, sizeof(serverAddress));
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);
    serverAddress.sin_port = htons(PORT);

    // 绑定服务器端socket和地址
    if (bind(serverSocket, (SOCKADDR *)&serverAddress, sizeof(serverAddress)) == SOCKET_ERROR)
    {
        printf("Bind server socket failed!\n");
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    // 监听客户端连接请求
    if (listen(serverSocket, SOMAXCONN) == SOCKET_ERROR)
    {
        printf("Listen server socket failed!\n");
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    printf("Server started!\n");

    while (1)
    {
        // 等待客户端连接
        clientSocket = accept(serverSocket, (SOCKADDR *)&clientAddress, &clientAddressLength);
        if (clientSocket == INVALID_SOCKET)
        {
            printf("Accept client socket failed!\n");
            closesocket(serverSocket);
            WSACleanup();
            return 1;
        }

        printf("Client connected!\n");

        // 接收客户端发送的数据
        bufferLength = recv(clientSocket, buffer, MAX_BUFF_SIZE, 0);
        if (bufferLength == SOCKET_ERROR)
        {
            printf("Receive data failed!\n");
            closesocket(clientSocket);
            continue;
        }

        buffer[bufferLength] = '\0';

        printf("Received file name: %s\n", buffer);

        // 打开指定文件
        FILE *file = fopen(buffer, "rb");
        if (file == NULL)
        {
            printf("File not found!\n");
            closesocket(clientSocket);
            continue;
        }

        // 发送文件内容
        while ((bufferLength = fread(buffer, sizeof(char), MAX_BUFF_SIZE, file)) > 0)
        {
            send(clientSocket, buffer, bufferLength, 0);
        }

        fclose(file);
        closesocket(clientSocket);
        printf("File sent!\n");
    }

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

    return 0;
}

客户端代码：

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

#define SERVER_ADDRESS "127.0.0.1"
#define PORT 12345
#define MAX_BUFF_SIZE 1024

int main()
{
    WSADATA wsaData;
    SOCKET clientSocket;
    SOCKADDR_IN serverAddress;
    char buffer[MAX_BUFF_SIZE];
    int bufferLength = 0;

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

    // 创建客户端socket
    if ((clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
    {
        printf("Create client socket failed!\n");
        WSACleanup();
        return 1;
    }

    // 设置服务器端地址
    ZeroMemory(&serverAddress, sizeof(serverAddress));
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_addr.s_addr = inet_addr(SERVER_ADDRESS);
    serverAddress.sin_port = htons(PORT);

    // 连接服务器端
    if (connect(clientSocket, (SOCKADDR *)&serverAddress, sizeof(serverAddress)) == SOCKET_ERROR)
    {
        printf("Connect to server failed!\n");
        closesocket(clientSocket);
        WSACleanup();
        return 1;
    }

    printf("Connected to server!\n");

    // 输入传输文件名
    printf("Please enter the file name: ");
    scanf("%s", buffer);

    // 发送传输文件名
    bufferLength = strlen(buffer);
    send(clientSocket, buffer, bufferLength, 0);

    // 接收服务器端发送的数据
    FILE *file = fopen(buffer, "wb");
    if (file == NULL)
    {
        printf("Create file failed!\n");
        closesocket(clientSocket);
        WSACleanup();
        return 1;
    }

    while ((bufferLength = recv(clientSocket, buffer, MAX_BUFF_SIZE, 0)) > 0)
    {
        fwrite(buffer, sizeof(char), bufferLength, file);
    }

    fclose(file);
    closesocket(clientSocket);

    printf("File received!\n");

    // 关闭Winsock
    WSACleanup();

    return 0;
}

以上代码中，服务器端会等待客户端连接，并接收客户端发送的文件名。如果文件存在，服务器端会将文件内容发送给客户端；如果文件不存在，则会断开连接。客户端会先输入要传输的文件名，然后连接服务器端并发送文件名。客户端会等待服务器端发送文件内容，并将其保存到本地。

当然，以上代码只是一个简单的示例，实际应用中还需要考虑数据的安全性、传输的效率等问题。