Java，SSLSocket，未收到答案

Question

I'm trying to use SSL with IMAP in java. I do not want to use the IMAP class. For some reason, when I send the n th message, I receive the answer to message n-2, and not to message n-1. Which means that I don't receive any answer to the first message sent until I send the second message. Can anyone spot what's wrong in the following minimal code ? (It is indeed minimal, apart from the println, which, I guess, help debugging)

import java.io.*;
import javax.net.ssl.*;
public class Mail{
    static String server = "imap.gmail.com";
    static String user   = "straightouttascript@gmail.com";
    static String pass   = "azerty75";
    public static void print (PrintWriter to, String text){
        System.out.println("sent : "+text);
        to.println(text+ "\r");
        to.flush();
    }

    public static void read  (BufferedReader from) throws InterruptedException, IOException {
        do {
            String line = from.readLine();
            System.out.println("received: "+line);
        } while (from.ready());
    }

    public static void main(String[] args){
        try{
            SSLSocket sslsocket = (SSLSocket) SSLSocketFactory.getDefault().createSocket(server, 993);
            System.out.println("Start connexion");

            BufferedReader from = new BufferedReader(new InputStreamReader(sslsocket.getInputStream()));
            //             read(from);

            PrintWriter to = new PrintWriter(new BufferedWriter(new OutputStreamWriter(sslsocket.getOutputStream())), true);
            print(to,"a1 login "+user+" "+pass);
            read(from);/*exepcted:
                         OK gimap ready 
                         a1 OK login@host authenticated (Success)*/

            sslsocket.close();
            System.out.println("End connexion");
        }

        catch (Exception e){ 
            e.printStackTrace();
        }
    } 
}

Answer 1

IMAP is not a pingpong protocol. The server doesn't send one line in response to one of yours.

Rather, you send commands and the server sends information. The server is permitted to send you more information than you asked for, so you can get seven responses to one command, and you can even get a response without sending a command at all, which is then called an unsolicited response. Strange phrase. Unsolicited responses are used by some servers to notify you about new mail, by more to notify you about flag changes on messages, and by (almost?) all to notify you that they're about to close your connection.