More fixes... it seems broadly usefulish now

- Increment bytes required for every extra VBI byte we learn about
- If sock is null, don't look at sock.connection
- Set sock to null after close
- Don't read from sock unless we need some bytes
- If we already have some bytes, parse them

There's a couple hacks in here that should be refactored though.

exec/broker.js

@@ -915,7 +915,8 @@ MQTT.Connection.timeToDie = function() {
 MQTT.Connection.prototype.tearDown = function() {
 	var sock = this.sock;
 
-	this.sock.connection = null;
+	if (sock !== null)
+		this.sock.connection = null;
 	if (this.rx_listener !== null)
 		removeEventListener(this.rx_listener);
 	if (this.rx_once != null) {
@@ -928,6 +929,7 @@ MQTT.Connection.prototype.tearDown = function() {
 	}
 	this.sock = null;
 	sock.close();
+	this.sock = null;
 	if (this.broker.connected[this.client_id] !== undefined)
 		delete this.broker.connected[this.client_id];
 	if (this.will !== null) {
@@ -1904,14 +1906,16 @@ MQTT.Packet.parseRemaining = function(conn) {
 
 MQTT.Packet.newBytes = function() {
 	try {
-		var data = this.recv(16384);
-		this.connection.rx_once = null;
-		if (data == null) {
-			// Error, tear down connection...
-			this.connection.tearDown();
-			return;
+		if (this.connection.rx_buf.length < this.connection.rx_need) {
+			var data = this.recv(16384);
+			this.connection.rx_once = null;
+			if (data == null) {
+				// Error, tear down connection...
+				this.connection.tearDown();
+				return;
+			}
+			this.connection.rx_buf += data;
 		}
-		this.connection.rx_buf += data;
 		while (this.connection.rx_need && this.connection.rx_buf.length >= this.connection.rx_need) {
 			try {
 				this.connection.rx_callback(this.connection);
@@ -1925,6 +1929,9 @@ MQTT.Packet.newBytes = function() {
 		if (this.connection.rx_need) {
 			this.connection.rx_once = this.once('read', MQTT.Packet.newBytes);
 		}
+		else if(this.connection.rx_buf.length > 0) {
+			js.setImmediate(MQTT.Connection.rxPacket, this);
+		}
 		else if(this.connection.rx_once === null) {
 			this.connection.rx_once = this.once('read', MQTT.Connection.rxPacket);
 		}
@@ -1945,7 +1952,7 @@ MQTT.Packet.gotRemainingLengthByte = function(conn) {
 		}
 	}
 	else {
-		conn.rx_need = 1;
+		conn.rx_need++;
 	}
 };
 
@@ -1979,7 +1986,10 @@ MQTT.Packet.prototype.recv = function(sock) {
 		return;
 	sock.connection.rx_need = 1;
 	sock.connection.rx_callback = MQTT.Packet.gotTypeFlags;
-	sock.connection.rx_once = sock.once('read', MQTT.Packet.newBytes);
+	if (sock.connection.rx_buf.length > 0)
+		MQTT.Packet.newBytes.call(sock);
+	else
+		sock.connection.rx_once = sock.once('read', MQTT.Packet.newBytes);
 };
 
 MQTT.Packet.prototype.serialize = function() {