Unable to write TCP response data to variable

Question

Unable to write TCP response data to variable

The problem is [visibilty of object inside and asynchronous calls to functions] of exported model.

 exports.send = function(socket, req, callback) {

  req.external_response = {};                      //  initialize empty object

  client.connect(socket.Port, socket.IPAddress, function() {
    client.write(req.query);
  });

  client.on('data', function(data, req) {                                   
    req.external_response = data.toString('utf8');// assign response to it
                                        // console.log(req.external_response); gives out response
  });

  client.on('close', function() {
    client.destroy();
    callback();
  });
};

after send finishes and callback is executed i still have

req.external_response = {}

if I do

var tmp = "";
client.on('data', function(data) {
    tmp = data.toString('utf8');// assign response to it
                                // console.log(tmp); gives out 
  });
req.external_response = tmp;    // tmp 'undefined'

I tried various ways to get that data written into variable but no success so far, maybe there is something that I did not noticed/missed. any suggestions how can I write TCP response to a desired variable?

node.js
sockets
tcp

Answer 1

The first snippet doesn't work probably because of variables conflict:

exports.send = function(socket, req, callback) {

  req.external_response = {};

  client.on('data', function(data, req2) {   // <----- req2 !!!
    req.external_response = ...
  });

  client.on('close', function() {
    console.log(req.external_response);
    client.destroy();
    callback();
  });

};

The second snippet:

var tmp = "";
client.on('data', function(data) {
    tmp = data.toString('utf8');// assign response to it
                                // console.log(tmp); gives out 
  });
req.external_response = tmp;

won't work because you assign tmp to req.external_response before the callback assigns data to it.

Answer 2

Here are what I tried to reach what I want: (no result in all of'em)

1

var assignData = function(source, destination){
destination = source.toString('utf8');
callback();
};

 client.on('data', function(data) {
assignData(data,req.external_response);
});

2

client.on('data', function(data) {
req.external_response = data.toString('utf8');
callback();

});

call to .send(socket, req, callback)

var req = {query:'0000000082&ServiceID=2355&QueryCode=8080'};
sender.send(req, {}, done);