Return value, or stop script - node.js

Question

Helo,
i create API in Windows Azure Mobile service, In this api script i have function to connect the other service. I have problem how to return value or stop executable my script when i have good answer from service. Function process.exit(1), don't work.
function function1(item,response) {
var buf ='';
var net = require('net');
var HOST = 'xxxx.xxxx.xxxx.xxxx';
var PORT = xxx;
var client = new net.Socket();
client.setTimeout(100000, function() {
console.log("Timeout");
response.send(500, "Timeout");
});
client.connect(PORT, HOST, function() {
client.write(item + "\n");
client.on('data', function(data) {
buf = buf + data.toString('utf-8');
});
client.on('close', function() {
});
client.on('end', function() {
if (buf.length > 1) {
var result = JSON.parse(buf);
//if resulr.Aviable is true the functios should return result or send result and stop execiuting script
if ( result.Avaiable) {
response.send(200, result);
//now i wont't to respond answer to client or return my value(result)
console.log('Send data');
}
}
client.destroy();
});
});
}

Answer 1

One alternative is to have a flag which indicates whether a response has been sent or not. This way, when the first of the alternatives is reached, you can set the flag to true (possibly clearing the timeout so it doesn't linger more than it needs) and in all cases check whether the flag has been set before returning the response. Something along the lines of the code below:
function function1(item,response) {
var buf = '';
var net = require('net');
var HOST = 'xxxx.xxxx.xxxx.xxxx';
var PORT = xxx;
var client = new net.Socket();
var responseSent = false;
var timeoutHandler = client.setTimeout(100000, function() {
if (!responseSent) {
responseSent = true;
console.log("Timeout");
response.send(500, { error: "Timeout" });
}
});
client.connect(PORT, HOST, function() {
client.write(item + "\n");
client.on('data', function(data) {
buf = buf + data.toString('utf-8');
});
client.on('close', function(had_error) {
if (!responseSent) {
clearTimeout(timeoutHandler);
responseSent = true;
console.log('Socket closed');
response.send(500, { error: had_error ? 'Socket error' : 'unknown' });
}
});
client.on('end', function() {
if (!responseSent) {
responseSent = true;
clearTimeout(timeoutHandler);
if (buf.length > 1) {
try {
var result = JSON.parse(buf);
if (result.Available) {
response.send(200, result);
} else {
response.send(500, { error: 'Socket data is not available' });
}
} catch (ex) {
response.send(500, { error: 'error parsing JSON', exception: ex });
}
} else {
// We should always return a response
response.send(500, { error: 'No data read from socket' });
}
}
client.destroy();
});
});
}
Notice that since node.js runs on a single thread, you can assume that there will be no cases where the response is sent twice. Also, you should make sure that the response is always sent once - in the code you had, if there was a socket error, or if buf.length was not greater than 1, or if result.Avaiable was not true, then the timeout response would be sent, but you didn't need to wait for the whole (100 seconds) time to send that response.