diff --git a/README.md b/README.md
index 3b3d3ae47..eed1bfa02 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ var engine = require('engine.io')
 
 server.on('connection', function (socket) {
   socket.send('utf 8 string');
+  socket.send(new Buffer([0, 1, 2, 3, 4, 5])); // binary data
 });
 ```
 
@@ -67,6 +68,23 @@ httpServer.on('request', function (req, res) {
 </script>
 ```
 
+Sending and receiving binary
+
+```html
+<script src="/path/to/engine.io.js"></script>
+<script>
+  var socket = new eio.Socket('ws://localhost/');
+  socket.binaryType = 'blob'; // receives Blob instead of ArrayBuffer (default)
+  socket.on('open', function () {
+    socket.send(new Int8Array(5));
+    socket.on('message', function (data) {
+      // data instanceof Blob => true when receiving binary
+    });
+    socket.on('close', function () { });
+  });
+</script>
+```
+
 For more information on the client refer to the
 [engine-client](http://github.com/learnboost/engine.io-client) repository.
 
@@ -220,7 +238,7 @@ A representation of a client. _Inherits from EventEmitter_.
 - `message`
     - Fired when the client sends a message.
     - **Arguments**
-      - `String`: Unicode string
+      - `String` or `Buffer`: Unicode string or Buffer with binary contents
 - `error`
     - Fired when an error occurs.
     - **Arguments**
@@ -253,9 +271,10 @@ A representation of a client. _Inherits from EventEmitter_.
 ##### Methods
 
 - `send`:
-    - Sends a message, performing `message = toString(arguments[0])`.
+    - Sends a message, performing `message = toString(arguments[0])` unless
+      sending binary data, which is sent as is.
     - **Parameters**
-      - `String`: a string or any object implementing `toString()`, with outgoing data
+      - `String` | `Buffer` | `ArrayBuffer` | `ArrayBufferView`: a string or any object implementing `toString()`, with outgoing data, or a Buffer or ArrayBuffer with binary data. Also any ArrayBufferView can be sent as is.
       - `Function`: optional, a callback executed when the message gets flushed out by the transport
     - **Returns** `Socket` for chaining
 - `close`
diff --git a/lib/server.js b/lib/server.js
index 82511e2b5..84607f2ec 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -205,6 +205,11 @@ Server.prototype.handshake = function(transport, req){
 
   try {
     var transport = new transports[transport](req);
+    if (req.query && req.query.b64) {
+      transport.supportsBinary = false;
+    } else {
+      transport.supportsBinary = true;
+    }
   }
   catch (e) {
     sendErrorMessage(req.res, Server.errors.BAD_REQUEST);
@@ -282,6 +287,11 @@ Server.prototype.onWebSocket = function(req, socket){
     } else {
       debug('upgrading existing transport');
       var transport = new transports[req.query.transport](req);
+      if (req.query && req.query.b64) {
+        transport.supportsBinary = false;
+      } else {
+        transport.supportsBinary = true;
+      }
       this.clients[id].maybeUpgrade(transport);
     }
   } else {
diff --git a/lib/transports/polling-xhr.js b/lib/transports/polling-xhr.js
index dde63aa98..8bc1d50fa 100644
--- a/lib/transports/polling-xhr.js
+++ b/lib/transports/polling-xhr.js
@@ -5,6 +5,7 @@
 
 var Polling = require('./polling');
 var Transport = require('../transport');
+var debug = require('debug')('engine:polling-xhr');
 
 /**
  * Module exports.
@@ -36,9 +37,15 @@ XHR.prototype.__proto__ = Polling.prototype;
 
 XHR.prototype.doWrite = function(data){
   // explicit UTF-8 is required for pages not served under utf
+  var isString = typeof data == 'string';
+  var contentType = isString
+    ? 'text/plain; charset=UTF-8'
+    : 'application/octet-stream';
+  var contentLength = '' + (isString ? Buffer.byteLength(data) : data.length);
+
   var headers = {
-    'Content-Type': 'text/plain; charset=UTF-8',
-    'Content-Length': Buffer.byteLength(data)
+    'Content-Type': contentType,
+    'Content-Length': contentLength
   };
 
   // prevent XSS warnings on IE
diff --git a/lib/transports/polling.js b/lib/transports/polling.js
index 7b40bb9bc..72d435319 100644
--- a/lib/transports/polling.js
+++ b/lib/transports/polling.js
@@ -118,14 +118,16 @@ Polling.prototype.onDataRequest = function (req, res) {
     this.onError('data request overlap from client');
     res.writeHead(500);
   } else {
+    var isBinary = 'application/octet-stream' == req.headers['content-type'];
+
     this.dataReq = req;
     this.dataRes = res;
 
-    var chunks = ''
+    var chunks = isBinary ? new Buffer(0) : ''
       , self = this
 
     function cleanup () {
-      chunks = '';
+      chunks = isBinary ? new Buffer(0) : '';
       req.removeListener('data', onData);
       req.removeListener('end', onEnd);
       req.removeListener('close', onClose);
@@ -138,7 +140,11 @@ Polling.prototype.onDataRequest = function (req, res) {
     };
 
     function onData (data) {
-      chunks += data;
+      if (typeof data == 'string') {
+        chunks += data;
+      } else {
+        chunks = Buffer.concat([chunks, data]);
+      }
     };
 
     function onEnd () {
@@ -157,7 +163,7 @@ Polling.prototype.onDataRequest = function (req, res) {
     req.on('close', onClose);
     req.on('data', onData);
     req.on('end', onEnd);
-    req.setEncoding('utf8');
+    if (!isBinary) { req.setEncoding('utf8'); }
   }
 };
 
@@ -171,7 +177,7 @@ Polling.prototype.onDataRequest = function (req, res) {
 Polling.prototype.onData = function (data) {
   debug('received "%s"', data);
   var self = this;
-  parser.decodePayload(data, function(packet){
+  var callback = function(packet) {
     if ('close' == packet.type) {
       debug('got xhr close packet');
       self.onClose();
@@ -179,7 +185,9 @@ Polling.prototype.onData = function (data) {
     }
 
     self.onPacket(packet);
-  });
+  };
+
+  parser.decodePayload(data, callback);
 };
 
 /**
@@ -197,7 +205,10 @@ Polling.prototype.send = function (packets) {
     this.shouldClose = null;
   }
 
-  this.write(parser.encodePayload(packets));
+  var self = this;
+  parser.encodePayload(packets, this.supportsBinary, function(data) {
+    self.write(data);
+  });
 };
 
 /**
diff --git a/lib/transports/websocket.js b/lib/transports/websocket.js
index 5582c58fc..59b8eb7b1 100644
--- a/lib/transports/websocket.js
+++ b/lib/transports/websocket.js
@@ -83,15 +83,16 @@ WebSocket.prototype.onData = function (data) {
  */
 
 WebSocket.prototype.send = function (packets) {
+  var self = this;
   for (var i = 0, l = packets.length; i < l; i++) {
-    var data = parser.encodePacket(packets[i]);
-    debug('writing "%s"', data);
-    this.writable = false;
-    var self = this;
-    this.socket.send(data, function (err){
-      if (err) return self.onError('write error', err.stack);
-      self.writable = true;
-      self.emit('drain');
+    parser.encodePacket(packets[i], this.supportsBinary, function(data) {
+      debug('writing "%s"', data);
+      self.writable = false;
+      self.socket.send(data, function (err){
+        if (err) return self.onError('write error', err.stack);
+        self.writable = true;
+        self.emit('drain');
+      });
     });
   }
 };
diff --git a/test/jsonp.js b/test/jsonp.js
index 28ef65364..42e3935b7 100644
--- a/test/jsonp.js
+++ b/test/jsonp.js
@@ -115,6 +115,27 @@ describe('JSONP', function () {
         });
       });
     }); 
+
+    it('should arrive from server to client and back with binary data (pollingJSONP)', function(done) {
+      var binaryData = new Buffer(5);
+      for (var i = 0; i < 5; i++) binaryData[i] = i;
+      var engine = listen( { allowUpgrades: false, transports: ['polling'] }, function (port) {
+        var socket = new eioc.Socket('ws://localhost:' + port, { transports: ['polling'], forceJSONP: true, upgrade: false});
+        engine.on('connection', function (conn) {
+          conn.on('message', function (msg) {
+            conn.send(msg);
+          });
+        });
+
+        socket.on('open', function() {
+          socket.send(binaryData);
+          socket.on('message', function (msg) {
+            for (var i = 0; i < msg.length; i++) expect(msg[i]).to.be(i);
+            done();
+          });
+        });
+      });
+    });
   });
   
   describe('close', function () {
diff --git a/test/server.js b/test/server.js
index f5b81b247..7593b91af 100644
--- a/test/server.js
+++ b/test/server.js
@@ -63,7 +63,7 @@ describe('server', function () {
     it('should send the io cookie', function (done) {
       var engine = listen(function (port) {
         request.get('http://localhost:%d/engine.io/default/'.s(port))
-          .query({ transport: 'polling' })
+          .query({ transport: 'polling', b64: 1 })
           .end(function (res) {
             // hack-obtain sid
             var sid = res.text.match(/"sid":"([^"]+)"/)[1];
@@ -76,7 +76,7 @@ describe('server', function () {
     it('should send the io cookie custom name', function (done) {
       var engine = listen({ cookie: 'woot' }, function (port) {
         request.get('http://localhost:%d/engine.io/default/'.s(port))
-          .query({ transport: 'polling' })
+          .query({ transport: 'polling', b64: 1 })
           .end(function (res) {
             var sid = res.text.match(/"sid":"([^"]+)"/)[1];
             expect(res.headers['set-cookie'][0]).to.be('woot=' + sid);
@@ -833,6 +833,196 @@ describe('server', function () {
       });
     });
 
+    it('should arrive when binary data is sent as Int8Array (ws)', function (done) {
+      var binaryData = new Int8Array(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData[i] = i;
+      }
+
+      var opts = { allowUpgrades: false, transports: ['websocket'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['websocket'] })
+
+        engine.on('connection', function (conn) {
+          conn.send(binaryData);
+        });
+
+        socket.on('open', function () {
+          socket.on('message', function(msg) {
+            for (var i = 0; i < binaryData.length; i++) {
+              var num = msg.readInt8(i);
+              expect(num).to.be(i);
+            }
+            done();
+          });
+        });
+      });
+    });
+
+    it('should arrive when binary data is sent as Int32Array (ws)', function (done) {
+      var binaryData = new Int32Array(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData[i] = (i + 100) * 9823;
+      }
+
+      var opts = { allowUpgrades: false, transports: ['websocket'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['websocket'] })
+
+        engine.on('connection', function (conn) {
+          conn.send(binaryData);
+        });
+
+        socket.on('open', function () {
+          socket.on('message', function(msg) {
+            for (var i = 0, ii = 0; i < binaryData.length; i += 4, ii++) {
+              var num = msg.readInt32LE(i);
+              expect(num).to.be((ii + 100) * 9823);
+            }
+            done();
+          });
+        });
+      });
+    });
+
+    it('should arrive when binary data is sent as Int32Array, given as ArrayBuffer(ws)', function (done) {
+      var binaryData = new Int32Array(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData[i] = (i + 100) * 9823;
+      }
+
+      var opts = { allowUpgrades: false, transports: ['websocket'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['websocket'] })
+
+        engine.on('connection', function (conn) {
+          conn.send(binaryData.buffer);
+        });
+
+        socket.on('open', function () {
+          socket.on('message', function(msg) {
+            for (var i = 0, ii = 0; i < binaryData.length; i += 4, ii++) {
+              var num = msg.readInt32LE(i);
+              expect(num).to.be((ii + 100) * 9823);
+            }
+            done();
+          });
+        });
+      });
+    });
+
+    it('should arrive when binary data is sent as Buffer (ws)', function (done) {
+      var binaryData = Buffer(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData.writeInt8(i, i);
+      }
+
+      var opts = { allowUpgrades: false, transports: ['websocket'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['websocket'] });
+        
+        engine.on('connection', function (conn) {
+          conn.send(binaryData);
+        });
+
+        socket.on('open', function () {
+          socket.on('message', function(msg) {
+            for (var i = 0; i < binaryData.length; i++) {
+              var num = msg.readInt8(i);
+              expect(num).to.be(i);
+            }
+            done();
+          });
+        });
+      });
+    });
+
+    it('should arrive when binary data sent as Buffer (polling)', function (done) {
+      var binaryData = Buffer(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData.writeInt8(i, i);
+      }
+
+      var opts = { allowUpgrades: false, transports: ['polling'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['polling'] });
+
+        engine.on('connection', function (conn) {
+          conn.send(binaryData);
+        });
+
+        socket.on('open', function() {
+          socket.on('message', function(msg) {
+            for (var i = 0; i < binaryData.length; i++) {
+              var num = msg.readInt8(i);
+              expect(num).to.be(i);
+            }
+
+            done();
+          });
+        });
+      });
+    });
+
+    it('should arrive as ArrayBuffer if requested when binary data sent as Buffer (ws)', function (done) {
+      var binaryData = Buffer(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData.writeInt8(i, i);
+      }
+
+      var opts = { allowUpgrades: false, transports: ['websocket'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['websocket'] });
+        socket.binaryType = 'arraybuffer';
+
+        engine.on('connection', function (conn) {
+          conn.send(binaryData);
+        });
+
+        socket.on('open', function() {
+          socket.on('message', function(msg) {
+            expect(msg instanceof ArrayBuffer).to.be(true);
+            var intArray = new Int8Array(msg);
+            for (var i = 0; i < binaryData.length; i++) {
+              expect(intArray[i]).to.be(i);
+            }
+
+            done();
+          });
+        });
+      });
+    });
+
+    it('should arrive as ArrayBuffer if requested when binary data sent as Buffer (polling)', function (done) {
+      var binaryData = Buffer(5);
+      for (var i = 0; i < binaryData.length; i++) {
+        binaryData.writeInt8(i, i);
+      }
+
+      var opts = { allowUpgrades: false, transports: ['polling'] };
+      var engine = listen(opts, function(port) {
+        var socket = new eioc.Socket('ws://localhost:%d'.s(port), { transports: ['polling'] });
+        socket.binaryType = 'arraybuffer';
+
+        engine.on('connection', function (conn) {
+          conn.send(binaryData);
+        });
+
+        socket.on('open', function() {
+          socket.on('message', function(msg) {
+            expect(msg instanceof ArrayBuffer).to.be(true);
+            var intArray = new Int8Array(msg);
+            for (var i = 0; i < binaryData.length; i++) {
+              expect(intArray[i]).to.be(i);
+            }
+
+            done();
+          });
+        });
+      });
+    });
+
+
     it('should trigger a flush/drain event', function(done){
       var engine = listen({ allowUpgrades: false }, function(port){
         engine.on('connection', function(socket){