Why my program is going on Infinite loop when i am trying to read multiple line input from TCP Server

Question

This is my TCP client java code:

socket = new Socket("127.0.0.1", 8088);
out = new DataOutputStream(socket.getOutputStream());
inputStream = socket.getInputStream();
inputReader = new BufferedReader(new InputStreamReader(inputStream));
String result = "";
while (inputStream != null) {
    result += inputReader.readLine();
}
out.writeUTF(result);
System.out.println(result);

socket.close();
out.close();

The while loop is getting executed infinitely.

I need a solution for this problem.

`inputStream` is never modified inside the loop, how and when should it become `null`? — Some programmer dude, Jan 23 '20 at 11:19

score 0 · Accepted Answer · answered Jan 24 '20 at 02:02

You need to check when readLine() returns null, not when inputStream becomes null (which it never will):

string s = inputReader.readLine();
while (s != null) {
    result += s;
    s = inputReader.readLine();
}

Or:

string s;
while ((s = inputReader.readLine()) != null) {
    result += s;
}

score -1 · Answer 2 · answered Jan 23 '20 at 11:24

-1

You need to nullify your inputStream within the while loop with some condition, for it to break.

answered Jan 23 '20 at 11:24

Sam

111
1
5

Avvappa Hegadyal · Answer 3 · 2020-01-24T07:18:15.440

-1

inputStream is always having a value i.e. its not null, so you keep looping and appending.

Does that make any sense? You can check like inputReader.readLine() != null instead:

string line;
while ((line=inputReader.readLine()) != null) {
    result += line;
}

edited Jan 24 '20 at 07:18

answered Jan 23 '20 at 11:27

Avvappa Hegadyal

275
1
7

You need to call `readLine()` once per loop iteration, not 2 times. – Remy Lebeau Jan 24 '20 at 02:01

Why my program is going on Infinite loop when i am trying to read multiple line input from TCP Server

3 Answers3