(Sockets) In java program pop3 commands only retrieve one message

Question

I wrote a java program without the javax.mail package. To connect to my Gmail account I am using socket. To retrieve my messages I'm using a for loop.

 for(int i=1; i<=NumOfMsg; i++){
   output.println("RETR "+i);
   do{
        answer = response();
        System.out.println(answer);
    } 
    while (true);   

response is method which look :

String response() throws IOException {

   response = input.readLine();
   if(response == null) 
   return null;
   else
   return answer;
}

When this program is conducted it only returns the first letter. After that the program won't repeat the loop. Cursor is blinking and I can't understand is he waiting another input of retr hanging. If I leave the program for 5 minutes it's starting eternal cycle and prints null.

Any suggestions would help.

Answer 1

Your logic is incorrect. You assign answer to the first result from response(), and then never update it, unless the response is null.

If you want to build an answer from the response, you should have a loop that appends the response to the answer variable.

for(int i = 1; i <= NumOfMsg; ++i){
   output.println("RETR " + i);
   do {
       answer = response();
       System.out.println(answer);
   }
   while (true);
}

String response() throws IOException {
   response = input.readLine();
   return response == null ? answer : answer + response;
}