Question

My problem is that I’m creating a FTP client, and so far its working flawlessly besides one minor detail, that keeps bugging me.
I need to know how many lines the FTP welcome message spans over… And this cannot be acceptable!

    private Socket connection;
    private PrintWriter outStream;
    private Scanner inStream;

public void InitiateConnection() throws IOException 
{
    log.Info(this, "Initiating connection to host: " + host + ":" + port);
    connection = new Socket(host, port);
    log.Info(this, "Connection initiated.");
    outStream = new PrintWriter(connection.getOutputStream(), true);
    inStream = new Scanner(connection.getInputStream());
    Listen();
    Listen();    
    Listen();
}

public String Listen() throws IOException
{
    if(connection == null)
        throw new IOException("Connection not initiated yet");
    String response = inStream.nextLine();
    log.Info(this, "Response: " + response);
    return response;
}

This is the simple setup, I have left out all other code, as it doesn’t have anything to do with my problem.

I have tried multiple things to try to achieve this.
Failed Solution 1:

String response = "";
while(response != null)
    Listen();

Failed Solution 2:

while(connection.getInputStream().available > 0)
    Listen();

And countless others… But either it doesn’t work, or the methods block and wait for new input. I have even tried with a timeout, but that doesn’t work flawlessly either, its not a proper solution to this problem…

I need to be able to get the entire welcome message from the FTP server, without knowing the amount of lines…
So I can both get this:

Response:   220-FileZilla Server version 0.9.39 beta
Response:   220-written by Tim Kosse ([e-mail])
Response:   220 Please visit http://sourceforge.net/projects/filezilla/

And this:

Response:   220-FileZilla Server version 0.9.40 beta
Response:   220 Welcome to Andrés FTP Server

Answer 1

If you have a close look at the messages, you see that all but the last lines have a - behind the status code. The last line has a , however, indicating, well, the last line.

You can read that in RFC 959, section 4.2:

Thus the format for multi-line replies is that the first line
will begin with the exact required reply code, followed
immediately by a Hyphen, “-” (also known as Minus), followed by
text. The last line will begin with the same code, followed
immediately by Space , optionally some text, and the Telnet
end-of-line code.

There is nothing said about the 2nd to second-last line, but it is logical that they have the same format as the 1st one.

---

Update: The FTP protocol seems to be badly documented, but I found another reference stating the same as me above:

The TCP/IP Guide mentions that

It is possible for a reply to contain more than one line of text. In this case, each line starts with the reply code, and all lines but the last have a hyphen between the reply code and the reply text, to indicate that the reply continues. The last line has a space between the reply code and reply text, just like a single-line reply. This facility is often used to provide additional response information after a user logs in, via the 230 reply code.