Question

I’m sending data from client sockets through a proxy server to an http server. When I post this data from proxy server to http, everything works fine, but if I close the http server, the proxy server dies.

I thought the post.end() function would close the request, but apparently not?! Do I have to do some callback magic?

I’ve attached my console output below, but here’s a brief explanation of the steps:

1. start server: node –harmony_weakmaps server.js
2. start api(http server): node api.js
3. start a client(telnet localhost 5280)
4. client connect message: {“m”:”connect”,”id”:”123″}
5. client message to api: {“m”:”x”,”id”:”123″}
6. kill api process- it blows up

console(server):

>>node --harmony_weakmaps server.js
Starting heartbeat
TCP server listening on 127.0.0.1:5280
HTTP server listening on 127.0.0.1:9002
Connection from 127.0.0.1:49356 id:undefined
received data: {"m":"connect","id":"123"}

id: 123
m: connect
associating uid 123 with socket [object Object]


Heartbeat Time: Tue Feb 14 2012 15:27:08 GMT-0800 (PST)
received data: {"m":"x","id":"123"}

id: 123
m: x
Invalid JSON:{"m":"x","id":"123"}

events.js:48
        throw arguments[1]; // Unhandled 'error' event
                       ^
Error: socket hang up
    at createHangUpError (http.js:1104:15)
    at Socket.onend (http.js:1181:27)
    at TCP.onread (net.js:369:26)

console(client, telnet):

>>telnet localhost 5280
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
>>{"m":"connect","id":"123"}
{"m":"connect","id":"123","success":"true"}
{"m":"pulse"}
>>{"m":"x","id":"123"}
{"success":"false","response":"invalid JSON"}
Connection closed by foreign host.

console(api):

>>node api.js 
API (HTTP server) listening on 127.0.0.1:8081
Request received: m=x&id=123&success=true
id: 123
m: x
// Then I close it (^C)

server.js(tcp-ip server that posts data from sockets to an http server):

// Launch Instructions
// node --harmony server.js

var net = require('net'); // tcp-server
var http = require("http"); // http-server

// Map of sockets to devices
var id2socket = new Object;
var socket2id = new WeakMap; // allows us to use object as key to hash

// HTTP:POST outbound function
// http://www.theroamingcoder.com/node/111
function postOut(dataToPost){
    var querystring = require('querystring');
    var http = require('http');

    var post_domain = 'localhost';
    var post_port = 8081;
    var post_path = '/';

    var post_data = querystring.stringify(dataToPost);

    var post_options = {
      host: post_domain,
      port: post_port,
      path: post_path,
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Content-Length': post_data.length
      }
    };

    var post_req = http.request(post_options, function(res) {
      res.setEncoding('utf8');
      res.on('data', function (chunk) {
        console.log('Response: ' + chunk);
      });
    });

    // write parameters to post body
    post_req.write(post_data);
    post_req.end();
    request.on("response", function (response) {
        console.log(response);
    });
}

function removeSocketFromMap(id,socket){
    console.log("removeSocketFromMap socket:"+socket+" id:"+id);
    delete id2socket[id];
    socket2id.delete(socket);
    //TODO: print map???
}

// Setup a tcp server
var server_plug = net.createServer(

    function(socket) {
        // Event handlers
        socket.addListener("connect", function(conn) {
            console.log("Connection from " + socket.remoteAddress + ":" + socket.remotePort + " id:"+socket.id );   
        });

        socket.addListener("data", function(data) {
            console.log("received data: " + data);
            try {
                request = JSON.parse(data);

                response = request;
                if(request.m !== undefined && request['id'] !== undefined){ // hack on 'id', id is js obj property
                    console.log("id: "+request['id']);
                    console.log("m: "+request.m);
                    if(request.m == 'connect'){
                        console.log("associating uid " + request['id'] + " with socket " + socket);
                        id2socket[request['id']] = socket;
                        socket2id.set(socket, request['id']);
                        response.success = 'true';
                    } else {
                        response.success = 'true';

                        postOut(request)
                    }
                }
                socket.write(JSON.stringify(response));
            } catch (SyntaxError) {
                console.log('Invalid JSON:' + data);
                socket.write('{"success":"false","response":"invalid JSON"}');
            }
        });

        socket.on('end', function() {
            id = socket2id.get(socket);
            console.log("socket disconnect by id " + id);
            removeSocketFromMap(id,socket);
        });

        socket.on('timeout', function() {
            console.log('socket timeout');
        });

    }
);

// Setup http server
var server_http = http.createServer(
    // Function to handle http:post requests, need two parts to it
    // http://jnjnjn.com/113/node-js-for-noobs-grabbing-post-content/
    function onRequest(request, response) {
        request.setEncoding("utf8");
        request.content = '';

        request.addListener("data", function(chunk) {
            request.content += chunk;
        });

        request.addListener("end", function() {
            console.log("Request received: "+request.content);

            try {
                var json = JSON.parse(request.content);
                var id = json['id'];
                var m = json['m'];
                console.log("id: "+id);
                console.log("m: "+m);

                // TODO: refactor this into another function
                try {
                    var socket = id2socket[id];
                    socket.write('{"m":"post"}');
                } catch (Error) {
                    console.log("Cannot find socket with id "+id);
                }

            } catch(Error) {
                console.log("JSON parse error: "+Error)
            }
        });
    }
);

// Heartbeat function
console.log("Starting heartbeat");
var beat_period = 20;
setInterval(function() {
    console.log("Heartbeat Time: " + new Date());
    for(var id in id2socket) {
        var socket = id2socket[id];
        try {
            socket.write('{"m":"pulse"}');
        } catch(Error) {
            removeSocketFromMap(id,socket);
        }

    }
}, beat_period * 1000);




// Fire up the servers
var HOST = '127.0.0.1';
var PORT = 5280;
var PORT2 = 9002;

// accept tcp-ip connections
server_plug.listen(PORT, HOST);
console.log("TCP server listening on "+HOST+":"+PORT);

// accept posts
server_http.listen(PORT2);
console.log("HTTP server listening on "+HOST+":"+PORT2);

api.js(http server):

var http = require("http"); // http-server
var querystring = require('querystring');

// Setup http server
var server_http = http.createServer(
    // Function to handle http:post requests, need two parts to it
    // http://jnjnjn.com/113/node-js-for-noobs-grabbing-post-content/
    function onRequest(request, response) {
        request.setEncoding("utf8");
        request.content = '';

        request.addListener("data", function(chunk) {
            request.content += chunk;
        });

        request.addListener("end", function() {
            console.log("Request received: "+request.content);

            try {
                // Parse incoming JSON
                var json = querystring.parse(request.content);
                var id = json['id'];
                var m = json['m'];
                console.log("id: "+id);
                console.log("m: "+m);

            } catch(Error) {
                console.log("JSON parse error: "+Error)
            }
        });
    }
);


// Fire up the servers
var HOST = '127.0.0.1';
var PORT = 8081;

server_http.listen(PORT);
console.log("API (HTTP server) listening on "+HOST+":"+PORT);

Answer 1

Silly me, I’m not up to speed on proper error handling in node. Fixing postOut() did the trick:

function postOut(dataToPost){

    var querystring = require('querystring');
    var http = require('http');

    var post_domain = 'localhost';
    var post_port = 8081;
    var post_path = '/';

    var post_data = querystring.stringify(dataToPost);

    var post_options = {
      host: post_domain,
      port: post_port,
      path: post_path,
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Content-Length': post_data.length
      }
    };

    var post_req = http.request(post_options, function(res) {
      res.setEncoding('utf8');
      res.on('data', function (chunk) {
        console.log('Response: ' + chunk);
      });
    });

    // Handle various issues
    post_req.on('error', function(error) { // <-------------------------------- Yeah Buddy!!!
        console.log('ERROR' + error.message);
        // If you need to go on even if there is an error add below line
        //getSomething(i + 1);
    });
    post_req.on("response", function (response) {
        console.log(response);
    });

    // write parameters to post body
    post_req.write(post_data);
    post_req.end();
    request.on("response", function (response) {
        console.log(response);
    });
}