Coping with variable sized reply from server

Question

Hi folks,
I've written a small class that acts as an SMTP client, opening a socket to a server and writing the appropriate SMTP commands out to it.
However, I've discovered that I sometimes get SMTP 554 (SMTP synchronization error) errors on this, and I think that I've tracked it down to the fact that after every write, I get a reply with a single readLine() call to the inputstream (well, a BufferedReader that I've wrapped around the inputstream) and according to the RFC, different numbers of lines of reply can be returned depending on the command sent.
I've been trying to figure out how to handle this but don't really even have a clue where to begin. I can't read lines until I get null, since the socket's not closed after the stream dries up, and I've tried using BufferedReader.isReady() to tell me when to stop, but if I do this, I seem to miss large chunks of the reply.
A sample of my code is:
        // open socket connection
        PrintWriter out;
        BufferedReader in;
        Socket skt;
        skt= new Socket(server, port);
        in=  new BufferedReader(new InputStreamReader(skt.getInputStream()));
        out= new PrintWriter(new BufferedOutputStream(skt.getOutputStream()), true);
        DateFormat df= DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.LONG, Locale.UK);
        // get the IP address of the machine that we're running on, for the HELO string
        InetAddress localhost= InetAddress.getLocalHost();
        String hostName= localhost.getHostAddress();
        // do initial handshaking
        String heloString= "HELO [" + hostName + "]";
        out.println(heloString);            replies= getReply(in) + "\n";
        out.println("MAIL FROM:" + from);   replies += getReply(in) + "\n";
        out.println("RCPT TO:" + to);       replies += getReply(in) + "\n";
        if (ccList != null)
            // send any (B)CCs
            for (int i=0; i<ccList.length; i++)
                out.println("RCPT TO:" + ccList);
replies += getReply(in) + "\n";
} // end loop
} // end if we have CCs
// send header
out.println("DATA"); replies += getReply(in) + "\n";
// ... send all the data ...
// terminate
out.println("."); replies += getReply(in) + "\n";
out.println("QUIT");
replies += getReply(in) + "\n";
// close connection
out.flush();
in.close();
out.close();
and the getReply method looks like this:
    /** gets reply from server and returns it */
    private String getReply(BufferedReader in)
        String line= null;
        StringBuffer lines= new StringBuffer();
        try
            /* --> this fails
            while (in.ready())
                line= in.readLine();
                lines.append(line + "\n");
            return lines.toString();
            line= in.readLine();
            System.out.println("line: " + line);
            System.out.println("leaving 'getReply'");
            return line;
            // System.out.println(line);
        } // end try clause
        catch (IOException i) {i.printStackTrace(); return null;}
    } // end method getReply()Any ideas?
Cheers,
Raj.

Answer 1

I think the BufferedReader.readline() call will block until data is available. That means that you can just keep calling readline(). This also means that the getReply(BufferedReader) method must run in a separate thread.