Windows下用c语言实现ftp的客户端和服务端的代码

以下是一个简单的基于C语言实现的FTP客户端和服务端的代码示例，运行在Windows系统上。

FTP客户端代码：

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

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

#define BUF_SIZE 1024
#define PORT 21

int main(int argc, char* argv[]) {
    if (argc != 3) {
        printf("Usage: %s <IP> <filename>\n", argv[0]);
        exit(1);
    }

    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("WSAStartup failed with error code %d\n", WSAGetLastError());
        exit(1);
    }

    // 创建套接字
    SOCKET sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock == INVALID_SOCKET) {
        printf("socket failed with error code %d\n", WSAGetLastError());
        exit(1);
    }

    // 填充服务端地址
    SOCKADDR_IN serverAddr;
    memset(&serverAddr, 0, sizeof(serverAddr));
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr(argv[1]);
    serverAddr.sin_port = htons(PORT);

    // 连接服务端
    if (connect(sock, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        printf("connect failed with error code %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        exit(1);
    }

    // 接收服务端欢迎信息
    char buf[BUF_SIZE];
    memset(buf, 0, BUF_SIZE);
    recv(sock, buf, BUF_SIZE, 0);
    printf("%s", buf);

    // 发送用户名和密码
    char user[] = "USER anonymous\r\n";
    send(sock, user, strlen(user), 0);
    memset(buf, 0, BUF_SIZE);
    recv(sock, buf, BUF_SIZE, 0);
    printf("%s", buf);

    char pass[] = "PASS \r\n";
    send(sock, pass, strlen(pass), 0);
    memset(buf, 0, BUF_SIZE);
    recv(sock, buf, BUF_SIZE, 0);
    printf("%s", buf);

    // 发送请求下载的文件名
    char retr[BUF_SIZE];
    sprintf(retr, "RETR %s\r\n", argv[2]);
    send(sock, retr, strlen(retr), 0);
    memset(buf, 0, BUF_SIZE);
    recv(sock, buf, BUF_SIZE, 0);
    printf("%s", buf);

    // 接收文件内容
    FILE* file = fopen(argv[2], "wb");
    int len;
    while ((len = recv(sock, buf, BUF_SIZE, 0)) > 0) {
        fwrite(buf, sizeof(char), len, file);
    }
    fclose(file);

    // 关闭套接字
    closesocket(sock);
    WSACleanup();
    return 0;
}

FTP服务端代码：

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

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

#define BUF_SIZE 1024
#define PORT 21

int main() {
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("WSAStartup failed with error code %d\n", WSAGetLastError());
        exit(1);
    }

    // 创建套接字
    SOCKET listenSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (listenSock == INVALID_SOCKET) {
        printf("socket failed with error code %d\n", WSAGetLastError());
        exit(1);
    }

    // 填充本地地址
    SOCKADDR_IN localAddr;
    memset(&localAddr, 0, sizeof(localAddr));
    localAddr.sin_family = AF_INET;
    localAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    localAddr.sin_port = htons(PORT);

    // 绑定套接字到本地地址
    if (bind(listenSock, (SOCKADDR*)&localAddr, sizeof(localAddr)) == SOCKET_ERROR) {
        printf("bind failed with error code %d\n", WSAGetLastError());
        closesocket(listenSock);
        WSACleanup();
        exit(1);
    }

    // 开始监听
    if (listen(listenSock, SOMAXCONN) == SOCKET_ERROR) {
        printf("listen failed with error code %d\n", WSAGetLastError());
        closesocket(listenSock);
        WSACleanup();
        exit(1);
    }

    printf("FTP server is listening on port %d...\n", PORT);

    // 接收连接请求并处理
    SOCKET connSock;
    SOCKADDR_IN clientAddr;
    int addrLen = sizeof(clientAddr);
    while (1) {
        connSock = accept(listenSock, (SOCKADDR*)&clientAddr, &addrLen);
        if (connSock == INVALID_SOCKET) {
            printf("accept failed with error code %d\n", WSAGetLastError());
            closesocket(listenSock);
            WSACleanup();
            exit(1);
        }

        printf("FTP client %s:%d connected\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));

        // 发送欢迎信息
        char welcome[] = "220 Welcome to FTP server\r\n";
        send(connSock, welcome, strlen(welcome), 0);

        // 接收用户名和密码
        char buf[BUF_SIZE];
        memset(buf, 0, BUF_SIZE);
        recv(connSock, buf, BUF_SIZE, 0);
        printf("%s", buf);

        memset(buf, 0, BUF_SIZE);
        recv(connSock, buf, BUF_SIZE, 0);
        printf("%s", buf);

        // 发送文件内容
        FILE* file = fopen("test.txt", "rb");
        int len;
        while ((len = fread(buf, sizeof(char), BUF_SIZE, file)) > 0) {
            send(connSock, buf, len, 0);
        }
        fclose(file);

        // 关闭连接套接字
        closesocket(connSock);
        printf("FTP client %s:%d disconnected\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));
    }

    // 关闭监听套接字并清理Winsock环境
    closesocket(listenSock);
    WSACleanup();
    return 0;
}