如何用C/C++编写FTP服务器代码？

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#define BUF_SIZE 1024
#define PORT 21
void error_handling(char *message);
int main(int argc, char *argv[])
{
    int sock;
    struct sockaddr_in serv_addr;
    char message[BUF_SIZE];
    int str_len;
    if (argc != 3)
    {
        printf("Usage: %s <IP> <port>
", argv[0]);
        exit(1);
    }
    sock = socket(PF_INET, SOCK_STREAM, 0);
    if (sock == 1)
        error_handling("socket() error");
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
    serv_addr.sin_port = htons(atoi(argv[2]));
    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == 1)
        error_handling("connect() error");
    str_len = read(sock, message, sizeof(message)  1);
    if (str_len == 1)
        error_handling("read() error");
    printf("Message from server: %s
", message);
    close(sock);
    return 0;
}
void error_handling(char *message)
{
    fputs(message, stderr);
    fputc('
', stderr);
    exit(1);
}

要编译并运行此代码，请将其保存为ftp_client.c，然后在命令行中执行以下命令：

gcc ftp_client.c o ftp_client
./ftp_client <server_ip> <server_port>

请将<server_ip>和<server_port>替换为您要连接的FTP服务器的实际IP地址和端口号。