Sending Message via DatagramChannel

Question

I am sending a message via a DatagramChannel as follows:

ByteBuffer buf = ByteBuffer.allocate(48);
buf.clear();
String request_message = "request";
buf.put(request_message.getBytes());
buf.flip();

int bytesSent = udpserver.send(buf, successor_port_1); // udpserver is a DatagramChannel

I then read the message on the server:

ByteBuffer buf = ByteBuffer.allocate(48);
buf.clear();

String message = new String(buf.array(), Charset.forName("UTF-8"));
System.out.println(message); //print message for testing purposes

if (message == "request"){
    //code here does not get executed
 }

The problem is, my code doesn't enter the "if" statement even though message = "request" which also seems to be confirmed by my print statement.

Any help would be appreciated!

String comparison has nothing to do with networking. String comparison is used everywhere. It should not be handeled as a TCP/IP specific feature. It is data marshaling feature. — Val, Apr 11 '13 at 16:37

score 1 · Accepted Answer · edited May 23 '17 at 12:22

The reason for this is that Strings in java need to be compared with .equals, so your test should be:

if (message.equals("request")){

This is because, in Java, == tests whether two object are the same instance (it tests reference equality - do both the references point to the same memory) rather than equal.

You can carry out a quick test:

System.out.println("request" == new String("request"));

Output:

false

For more information read this SO answer.

Sending Message via DatagramChannel

1 Answers1