node.js websocket send custom data

Question

I found a great websocket tutorial. If the server get a message, then the server decodes it, and writes to the console, and after that the server sends it back to the client.

  var firstByte = data[0],  
      secondByte = data[1];

  if(!(firstByte & 0x81)) socket.end();
  if(!(secondByte & 0x80)) socket.end();

  var length = secondByte & 0x7f;

  if(length < 126){  
    var mask = data.slice(2,6);  
    var text = data.slice(6);  
  }  

  if(length == 126){  
    var mask = data.slice(4,8);
    var text = data.slice(8);  
  }

  var unMaskedText = new Buffer(text.length);  
    for(var i=0;i<text.length;i++){  
      unMaskedText[i] = text[i] ^ mask[i%4];  
  }  

  console.log(unMaskedText.toString());

  if(unMaskedText.length > 125)  
   var newFrame = new Buffer(4);  
  else  
   var newFrame = new Buffer(2);

  newFrame[0] = 0x81; 

  if(unMaskedText.length > 125){  

  newFrame[1] = 126;  

  var length = unMaskedText.length;  

  newFrame[2] = length >> 8;  
  newFrame[3] = length & 0xFF; //1111 1111  


  } else {  

  newFrame[1] = unMaskedText.length;  

  socket.write(newFrame, 'binary');  
  socket.write(unMaskedText, 'utf8');  
  }

It works, but I would like to send custom messages, not just what the client sent me.

Perhaps you find this wiki answer interesting: stackoverflow.com/questions/8125507/…. — pimvdb
– pimvdb, Commented Nov 21, 2011 at 16:24
Looking at it, why can't you send something else than unMaskedText instead? E.g. just overwrite unMaskedText before doing the send calculations. — pimvdb
– pimvdb, Commented Nov 21, 2011 at 16:37
after console.log... I wrote unMaskedText = "welcome"; it works, but when I use some special character, then it crashes. for example: unMaskedText = "welcome: ő"; — Uw001
– Uw001, Commented Nov 21, 2011 at 16:46
Oops, I meant new Buffer("welcome ..."). That should take care of encoding. — pimvdb
– pimvdb, Commented Nov 21, 2011 at 16:52

pimvdb · Accepted Answer · 2012-03-24 16:39:24Z

1

I'll post it as an answer just for clarity.

You should change unMaskedText to a buffer representing the text you want to send, after displaying the received data but before doing calculations for the data to send. E.g.

unMaskedText = new Buffer("test");

edited Mar 24, 2012 at 16:39

answered Nov 21, 2011 at 17:48

pimvdb

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