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copied!<p>All methods in twisted are <em>asynchronous</em>. All of the the methods such as <code>connectionMade</code> and <code>lineReceived</code> are happening on the same thread. The Twisted reactor runs a loop (called an <em>event loop</em>) and it calls methods such as <code>connectionMade</code> and <code>lineReceived</code> when these events happen.</p> <p>You have an infinite loop in <code>connectionMade</code>. Once Python gets into that loop, it can never get out. Twisted calls <code>connectionMade</code> when connection is established, and your code stays there forever. Twisted has no opportunity to actually write the data to the transport, or receive data, it is stuck in <code>connectionMade</code>!</p> <p>When you write Twisted code, the important point that you must understand is that you may not <em>block</em> on the Twisted thread. For example, let's say I want to send a "Hello" 4 seconds after a client connects. I might write this:</p> <pre><code>class EchoClient(LineReceiver): def connectionMade(self): time.sleep(4) self.transport.write("Hello") </code></pre> <p>but this would be wrong. What happens if 2 clients connect at the same time? The first client will go into <code>connectionMade</code>, and my program will hang for 4 seconds until the "Hello" is sent.</p> <p>The Twisted way to do this would be like this:</p> <pre><code>class EchoClient(LineReceiver): def connectionMade(self): reactor.callLater(4, self.sendHello) def sendHello(self): self.transport.write("Hello") </code></pre> <p>Now, when Twisted enters <code>connectionMade</code>, it calls <code>reactor.callLater</code> to <em>schedule</em> an event 4 seconds in the future. Then it exits <code>connectionMade</code> and continues doing all the other stuff it needs to do. Until you grasp the concept of async programming you can't continue in Twisted. I suggest you read through the <a href="https://twistedmatrix.com/documents/current/core/howto/index.html" rel="nofollow">Twisted docs here</a>.</p> <p>Finally, an unrelated note: If you have a <code>LineReceiver</code>, you should not implement your own <code>dataReceived</code>, it will make <code>lineReceived</code> not called. <code>LineReceiver</code> is a protocol which implements its own <code>dataReceived</code> which buffers and breaks up data into lines and calls <code>lineReceived</code> methods.</p>

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