Listen for FTP Messages

Getting Help
1

I am trying to establish a ftp connection with a server. I can start the connection and send messages but I’m having trouble listening for and reading responses. Is there a way to listen passively on an active TCPConn connection or do I need something else? package main

import (

    "fmt"

    "net"

    "os"

)

func main() {

    // Error if number of arguments doesn't match

    if len(os.Args) < 2 {

        fmt.Fprintf(os.Stderr, "Usage:%s host:port", os.Args[0])

        os.Exit(1)

    }

    // The service in form of a string

    //(here the ipv4 address and port number X.X.X.X:PN)

    service := os.Args[1]

    // Create TCPAddr from the service string

    tcpAddr, err := net.ResolveTCPAddr("tcp4", service)

    checkError(err)

    // Create TCP connection

    conn, err := net.DialTCP("tcp", nil, tcpAddr)

    checkError(err)

    // Send query to FTP server

    _, err = conn.Write([]byte("USER admin\r\n"))

    checkError(err)

    // Read from the FTP server

    result, err = ioutil.ReadAll(conn)

    checkError(err)

    // Close Connection

    conn.Close()

    // Print Results

    fmt.Println(string(result))

    os.Exit(0)

}

func checkError(err error) {

    if err != nil {

        fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())

        os.Exit(1)

    }

}
2

Show us the relevant parts of your code.

3

Here it is. I can send commands and arguments to the server but ReadAll doesn’t catch the reply. I want to be able to print the replies from the server.

4

Which ftp third party package are you using ?

5

Why don’t you take a look at the existing FTP libraries? See https://github.com/avelino/awesome-go/blob/master/README.md#networking

6

I’m not using a third-party package. I know there are some ftp packages on github but I’m making this program as a test for a future application for which I will have to make custom massages and using an external library kinda defeats the point.

7

What is the result of this method call? What does result contain?

8

According to the documentation it should return a []byte, but that is where the program gets stuck. Earlier I tried a program which used the HEAD http message and it worked.

9

My guess is that readall expects something to either run out of bytes or end with for example \0 or \n. Try reading only a few bytes and see if you do get a response at all.

10

Per documentation it reads until EOF:

ReadAll reads from r until an error or EOF and returns the data it read.

So “runs out of bytes” is probably the most correct phrase.

11

It seems so I replaced message reading using bufio.NewReader (dont know if this is the optimal solution) and now it works fine.

12

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