Send command to FTP server using sockets in C

Question

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 [email protected]";

    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;
}

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.

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

I should get "331 User [email protected] OK. Password required" message? — amone
– amone, Commented Mar 31, 2015 at 20:17
The best thing you can do to debug your sockets application is to set up a simple local server with netcat and see all of the messages being received and sent (it's a general advice). — Eugene Sh.
– Eugene Sh., Commented Mar 31, 2015 at 20:18

Jim Lewis · Accepted Answer · 2015-03-31 20:17:45Z

3

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.

Source: RFC 959

answered Mar 31, 2015 at 20:17

Jim Lewis

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