linuxC语言实现ftp服务

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define PORT 21
#define BUFFER_SIZE 1024

void handle_client(int client_fd) {
    char buffer[BUFFER_SIZE];
    int bytes_received;

    while (1) {
        bytes_received = recv(client_fd, buffer, BUFFER_SIZE, 0);
        if (bytes_received <= 0) {
            break;
        }

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

        // 处理FTP命令
        if (strncmp(buffer, "USER", 4) == 0) {
            send(client_fd, "331 User name okay, need password.\r\n", 36, 0);
        } else if (strncmp(buffer, "PASS", 4) == 0) {
            send(client_fd, "230 User logged in, proceed.\r\n", 30, 0);
        } else if (strncmp(buffer, "QUIT", 4) == 0) {
            send(client_fd, "221 Goodbye.\r\n", 14, 0);
            break;
        } else {
            send(client_fd, "500 Syntax error, command unrecognized.\r\n", 42, 0);
        }
    }

    close(client_fd);
}

int main() {
    int server_fd, client_fd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t addr_len = sizeof(client_addr);

    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(PORT);

    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind");
        close(server_fd);
        exit(EXIT_FAILURE);
    }

    if (listen(server_fd, 5) < 0) {
        perror("listen");
        close(server_fd);
        exit(EXIT_FAILURE);
    }

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

    while (1) {
        client_fd = accept(server_fd, (struct sockaddr *)&client_addr, &addr_len);
        if (client_fd < 0) {
            perror("accept");
            continue;
        }

        printf("Accepted connection from %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
        handle_client(client_fd);
    }

    close(server_fd);
    return 0;
}