Why is the socket.remoteAddress event undefined on 'end'?

Question

I have a simple TCP server:

var net = require('net'); var PORT = 6346; var server = net.createServer(function(socket) { socket.on('connect', function() { console.log('Client connected: ' + socket.remoteAddress); socket.write('Welcome to the server!\r\n'); }); socket.on('end', function() { console.log('Client disconnected: ' + socket.remoteAddress); }); socket.on('error', function() { console.log('Client error: ' + socket.remoteAddress); }); socket.on('timeout', function() { console.log('Client timed out:' + socket.remoteAddress); }); }).listen(PORT); 

When I connect to the server, I see the expected Client connected: 127.0.0.1 , but when I disconnect, I see Client disconnected: undefined . Why is socket.remoteAddress undefined and how can I register the client IP address when disconnected?

Answer 1

The problem is that after disconnecting the socket, some properties (such as remoteAddress ) are no longer available!

You can get around this by wrapping the socket with your own object, or by tracking this remote address somewhere else when connected. (Woot for closures.)

Answer 2

The remoteAddress property will be even after disconnecting after https://github.com/joyent/node/commit/8c38b07252d86f4eef91344f8df4f0c3e38bca35 is in the stable version of Node.js. io.js will have it in the next release: https://github.com/iojs/io.js/issues/1157

Answer 3

When I tried to debug 504 errors from specific servers, I found that changing this code

 request(url, function (error, response, body) { if (error) { callback(error); } else { if (response.statusCode == 200) { callback(null, body); } else { // response.connection.remoteAddress is undefined here callback(new Error("Non status 200: " + response.statusCode + " received from " + response.connection.remoteAddress + " when requesting " + url)); } } }); 

to this code

 request(url, function (error, response, body) { if (error) { callback(error); } else { if (response.statusCode == 200) { callback(null, body); } else { // response.connection.remoteAddress is now magically set somehow callback(new Error("Non status 200: " + response.statusCode + " received from " + response.connection.remoteAddress + " when requesting " + url)); } } }).on('response', function(response) { // This next line is very important. It seems to make the remoteAddress variable stay in the socket so we can read it. let remoteAddress = response.connection.remoteAddress; }); 

seemed to work. I have no idea why accessing the remoteAddress variable in the response handler forces it to remain in place for reading.