使用C中的套接字将命令发送到FTP服务器 [英] Send command to FTP server using sockets in C

问题描述

我是套接字编程的新手。我想登录到我的FTP服务器。我可以建立连接，但我无法发送其他用户名和密码的命令。

I am new to socket programing. I want to login to my ftp server. I can establish connection successfully but I can't send other commands for user and password.

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

int main(int argc, char *argv[])
{
    argv[0]="2";
    argv[1]="00.00.00.0000"; //my ip

    int sockfd = 0, n = 0;
    char recvBuff[1024];
    struct sockaddr_in serv_addr;
    char message[100]="USER [e-mail]";

    argc=2;

    if(argc != 2)
    {
        printf("\n Usage: %s <ip of server> \n",argv[0]);
        return 1;
    }

    memset(recvBuff, '0',sizeof(recvBuff));
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
        printf("\n Error : Could not create socket \n");
        return 1;
    }

    memset(&serv_addr, '0', sizeof(serv_addr));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(21);


    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);

    if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
    {
        printf("\n Error : Connect Failed \n");
        return 1;
    }

    if( send(sockfd , message , strlen(message) , 0) < 0)
    {
        perror("send failed");
        return 1;
    }


    while ( (n = read(sockfd, recvBuff, sizeof(recvBuff)-1)) > 0)
    {
        recvBuff[n] = 0;
        if(fputs(recvBuff, stdout) == EOF)
        {
            printf("\n Error : Fputs error\n");
            return 0;
        }
    }

    if(n < 0)
    {
        printf("\n Read error \n");
        return 0;
    } 

    return 0;
}

我得到这个：

I am getting this:

220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
220-You are user number 1 of 50 allowed.
220-Local time is now 22:05. Server port: 21.
220 You will be disconnected after 15 minutes of inactivity.

为什么我无法在建立连接后向服务器发送命令？

Why I can't send commands to server after connection established?

推荐答案

您需要使用CRLF终止每个FTP命令。这在USER命令中缺少。在收到换行符之前，远程服务器不会处理该命令。

You need to terminate each FTP command with a CRLF. This is missing from your USER command. The remote server won't process the command until it receives the newline.

来源： RFC 959

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