diff --git a/src/main/java/com/corundumstudio/socketio/handler/AuthorizeHandler.java b/src/main/java/com/corundumstudio/socketio/handler/AuthorizeHandler.java
index c8660fa..80bfe3f 100644
--- a/src/main/java/com/corundumstudio/socketio/handler/AuthorizeHandler.java
+++ b/src/main/java/com/corundumstudio/socketio/handler/AuthorizeHandler.java
@@ -35,6 +35,7 @@ import com.corundumstudio.socketio.HandshakeData;
 import com.corundumstudio.socketio.SocketIOClient;
 import com.corundumstudio.socketio.Transport;
 import com.corundumstudio.socketio.ack.AckManager;
+import com.corundumstudio.socketio.messages.HttpErrorMessage;
 import com.corundumstudio.socketio.namespace.Namespace;
 import com.corundumstudio.socketio.namespace.NamespacesHub;
 import com.corundumstudio.socketio.protocol.AuthPacket;
@@ -164,7 +165,7 @@ public class AuthorizeHandler extends ChannelInboundHandlerAdapter implements Di
 
         List<String> transportValue = params.get("transport");
         if (transportValue == null) {
-            log.warn("Got no transports for request {}", req.uri());
+            log.error("Got no transports for request {}", req.uri());
 
             HttpResponse res = new DefaultHttpResponse(HTTP_1_1, HttpResponseStatus.UNAUTHORIZED);
             channel.writeAndFlush(res).addListener(ChannelFutureListener.CLOSE);
@@ -172,11 +173,20 @@ public class AuthorizeHandler extends ChannelInboundHandlerAdapter implements Di
         }
 
         Transport transport = Transport.byName(transportValue.get(0));
+        if (!configuration.getTransports().contains(transport)) {
+            Map<String, Object> errorData = new HashMap<String, Object>();
+            errorData.put("code", 0);
+            errorData.put("message", "Transport unknown");
+            
+            channel.attr(EncoderHandler.ORIGIN).set(origin);
+            channel.writeAndFlush(new HttpErrorMessage(errorData));
+            return false;
+        }
+        
         ClientHead client = new ClientHead(sessionId, ackManager, disconnectable, storeFactory, data, clientsBox, transport, disconnectScheduler, configuration);
         channel.attr(ClientHead.CLIENT).set(client);
         clientsBox.addClient(client);
 
-
         String[] transports = {};
         if (configuration.getTransports().contains(Transport.WEBSOCKET)) {
             transports = new String[] {"websocket"};
diff --git a/src/main/java/com/corundumstudio/socketio/handler/EncoderHandler.java b/src/main/java/com/corundumstudio/socketio/handler/EncoderHandler.java
index 0e1cbce..bd063d8 100644
--- a/src/main/java/com/corundumstudio/socketio/handler/EncoderHandler.java
+++ b/src/main/java/com/corundumstudio/socketio/handler/EncoderHandler.java
@@ -29,6 +29,7 @@ import org.slf4j.LoggerFactory;
 
 import com.corundumstudio.socketio.Configuration;
 import com.corundumstudio.socketio.Transport;
+import com.corundumstudio.socketio.messages.HttpErrorMessage;
 import com.corundumstudio.socketio.messages.HttpMessage;
 import com.corundumstudio.socketio.messages.OutPacketMessage;
 import com.corundumstudio.socketio.messages.XHROptionsMessage;
@@ -37,6 +38,7 @@ import com.corundumstudio.socketio.protocol.Packet;
 import com.corundumstudio.socketio.protocol.PacketEncoder;
 
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufOutputStream;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFutureListener;
@@ -113,7 +115,8 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
                     .add(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE)
                     .add(HttpHeaderNames.ACCESS_CONTROL_ALLOW_HEADERS, HttpHeaderNames.CONTENT_TYPE);
 
-        addOriginHeaders(ctx.channel(), res);
+        String origin = ctx.channel().attr(ORIGIN).get();
+        addOriginHeaders(origin, res);
 
         ByteBuf out = encoder.allocateBuffer(ctx.alloc());
         sendMessage(msg, ctx.channel(), out, res, promise);
@@ -122,17 +125,20 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
     private void write(XHRPostMessage msg, ChannelHandlerContext ctx, ChannelPromise promise) {
         ByteBuf out = encoder.allocateBuffer(ctx.alloc());
         out.writeBytes(OK);
-        sendMessage(msg, ctx.channel(), out, "text/html", promise);
+        sendMessage(msg, ctx.channel(), out, "text/html", promise, HttpResponseStatus.OK);
     }
 
-    private void sendMessage(HttpMessage msg, Channel channel, ByteBuf out, String type, ChannelPromise promise) {
-        HttpResponse res = new DefaultHttpResponse(HTTP_1_1, HttpResponseStatus.OK);
+    private void sendMessage(HttpMessage msg, Channel channel, ByteBuf out, String type, ChannelPromise promise, HttpResponseStatus status) {
+        HttpResponse res = new DefaultHttpResponse(HTTP_1_1, status);
 
         res.headers().add(HttpHeaderNames.CONTENT_TYPE, type)
-                    .add(HttpHeaderNames.SET_COOKIE, "io=" + msg.getSessionId())
                     .add(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
+        if (msg.getSessionId() != null) {
+            res.headers().add(HttpHeaderNames.SET_COOKIE, "io=" + msg.getSessionId());
+        }
 
-        addOriginHeaders(channel, res);
+        String origin = channel.attr(ORIGIN).get();
+        addOriginHeaders(origin, res);
 
         HttpUtil.setContentLength(res, out.readableBytes());
 
@@ -150,7 +156,11 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
         channel.write(res);
 
         if (log.isTraceEnabled()) {
-            log.trace("Out message: {} - sessionId: {}", out.toString(CharsetUtil.UTF_8), msg.getSessionId());
+            if (msg.getSessionId() != null) {
+                log.trace("Out message: {} - sessionId: {}", out.toString(CharsetUtil.UTF_8), msg.getSessionId());
+            } else {
+                log.trace("Out message: {}", out.toString(CharsetUtil.UTF_8));
+            }
         }
 
         if (out.isReadable()) {
@@ -161,8 +171,16 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
 
         channel.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT, promise).addListener(ChannelFutureListener.CLOSE);
     }
+    
+    private void sendError(HttpErrorMessage errorMsg, ChannelHandlerContext ctx, ChannelPromise promise) throws IOException {
+        final ByteBuf encBuf = encoder.allocateBuffer(ctx.alloc());
+        ByteBufOutputStream out = new ByteBufOutputStream(encBuf);
+        encoder.getJsonSupport().writeValue(out, errorMsg.getData());
+
+        sendMessage(errorMsg, ctx.channel(), encBuf, "application/json", promise, HttpResponseStatus.BAD_REQUEST);
+    }
 
-    private void addOriginHeaders(Channel channel, HttpResponse res) {
+    private void addOriginHeaders(String origin, HttpResponse res) {
         if (version != null) {
             res.headers().add(HttpHeaderNames.SERVER, version);
         }
@@ -171,7 +189,6 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
             res.headers().add(HttpHeaderNames.ACCESS_CONTROL_ALLOW_ORIGIN, configuration.getOrigin());
             res.headers().add(HttpHeaderNames.ACCESS_CONTROL_ALLOW_CREDENTIALS, Boolean.TRUE);
         } else {
-            String origin = channel.attr(ORIGIN).get();
             if (origin != null) {
                 res.headers().add(HttpHeaderNames.ACCESS_CONTROL_ALLOW_ORIGIN, origin);
                 res.headers().add(HttpHeaderNames.ACCESS_CONTROL_ALLOW_CREDENTIALS, Boolean.TRUE);
@@ -200,6 +217,8 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
             write((XHROptionsMessage) msg, ctx, promise);
         } else if (msg instanceof XHRPostMessage) {
             write((XHRPostMessage) msg, ctx, promise);
+        } else if (msg instanceof HttpErrorMessage) {
+            sendError((HttpErrorMessage) msg, ctx, promise);
         }
     }
 
@@ -263,10 +282,10 @@ public class EncoderHandler extends ChannelOutboundHandlerAdapter {
             if (jsonpIndex == null) {
                 type = "text/plain";
             }
-            sendMessage(msg, channel, out, type, promise);
+            sendMessage(msg, channel, out, type, promise, HttpResponseStatus.OK);
         } else {
             encoder.encodePackets(queue, out, ctx.alloc(), 50);
-            sendMessage(msg, channel, out, "application/octet-stream", promise);
+            sendMessage(msg, channel, out, "application/octet-stream", promise, HttpResponseStatus.OK);
         }
     }
 
diff --git a/src/main/java/com/corundumstudio/socketio/messages/HttpErrorMessage.java b/src/main/java/com/corundumstudio/socketio/messages/HttpErrorMessage.java
new file mode 100644
index 0000000..fb1f3dd
--- /dev/null
+++ b/src/main/java/com/corundumstudio/socketio/messages/HttpErrorMessage.java
@@ -0,0 +1,18 @@
+package com.corundumstudio.socketio.messages;
+
+import java.util.Map;
+
+public class HttpErrorMessage extends HttpMessage {
+
+    private final Map<String, Object> data;
+
+    public HttpErrorMessage(Map<String, Object> data) {
+        super(null, null);
+        this.data = data;
+    }
+
+    public Map<String, Object> getData() {
+        return data;
+    }
+    
+}
diff --git a/src/main/java/com/corundumstudio/socketio/protocol/PacketEncoder.java b/src/main/java/com/corundumstudio/socketio/protocol/PacketEncoder.java
index e2ea26f..fe6b602 100644
--- a/src/main/java/com/corundumstudio/socketio/protocol/PacketEncoder.java
+++ b/src/main/java/com/corundumstudio/socketio/protocol/PacketEncoder.java
@@ -46,6 +46,10 @@ public class PacketEncoder {
         this.configuration = configuration;
     }
 
+    public JsonSupport getJsonSupport() {
+        return jsonSupport;
+    }
+    
     public ByteBuf allocateBuffer(ByteBufAllocator allocator) {
         if (configuration.isPreferDirectBuffer()) {
             return allocator.ioBuffer();