When you receive the message, use this:
if (receivedMessage.startsWith("/")) {
System.out.println("message: "+receivedMessage);
}
Just start debugging at the beginning; if the above code doesn't output anything, try outputting the message without an if statement. If it does go one step further. For example, in the if statement, put:
if (receivedMessage.startsWith("/#quit"))
. etc.