Cannot call method 'write' of undefined

Question

I am trying to make a client-like TCP socket on Node.js, and making it connect to a server:

this.socket = new net.Socket();
this.socket.setEncoding('UTF8');
this.socket.on('data', function(data)
{
    this.recvHHCPmsg(data);
});

this.socket.connect(9000, '192.198.94.227', function()
{
    //called when connection is created
    var loginCmd = 'login' + wSym + user + wSym + pass;
    console.log("Connected to HHCP server.");
    this.socket.write(loginCmd, 'UTF8', function(){ console.log('Data sent.'); });
});

But I get this error (at the 'this.socket.write' line):

TypeError: Cannot call method 'write' of undefined

From the function used when the connection is created, I can tell that it is recognizing the host and connecting. So why can't I send data with the socket?

EDIT: This problem has been solved, but there's a new one...

Okay, but I need code inside the call-back function to be able to access the object which 'owns' the socket object:
this.socket.on('data', function(data) //'this' is referring to the 'User' object
{
    this.recvHHCPmsg(data); //'this' is referring to the socket.
    //The 'User' object has a method called 'recvHHCPmsg'. 
    //I want to call that function from within this call-back function.
});

Is there any way to do things with the object that the socket belongs to?

This is how the recvHHCPmsg() function is defined:

User.prototype.recvHHCPmsg = 
function(text)
{
    if (text == 'disconnect')
    {
        this.socket.write('disconnect');
        this.socket.end();
        this.socket.destroy();
    }
};

possible duplicate of [Javascript callbacks losing 'this'](http://stackoverflow.com/questions/10766407/javascript-callbacks-losing-this) — Quentin, Sep 29 '13 at 18:29

thefourtheye · Accepted Answer · 2013-09-29T19:05:46.757

0

Change

this.socket.write

to

this.write

Inside the function call, the current object pointed by this is the socket object only. When I tried on my local machine just with this change, I got

Connected to HHCP server.
Data sent.

EDIT:

To make recvHHCPmsg accessible, do the following.

Change

this.socket.on('data', function(data) {
    this.recvHHCPmsg(data);
});

to

var self = this;
this.socket.on('data', function(data) {
    self.recvHHCPmsg(data);
});

edited Sep 29 '13 at 19:05

answered Sep 29 '13 at 18:29

thefourtheye

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Thank you for helping me with that problem, but I have a new question. See my first post. I edited it. – hammereditor Sep 29 '13 at 18:48
@hammereditor Please show how and where `recvHHCPmsg` defined. – thefourtheye Sep 29 '13 at 18:51
Okay, I did. Again, it's in the first post. – hammereditor Sep 29 '13 at 18:55
Yes, it is. Inside the callback, I want it to call the 'recvHHCPmsg' of the User object. – hammereditor Sep 29 '13 at 19:02

Cannot call method 'write' of undefined

EDIT: This problem has been solved, but there's a new one...

1 Answers1