I am trying to open a sender / receiver socket on the same device and send a 64k packet to the router then receive it back. The key is packet should go through router. So I will be able to tell user something about his local wifi speed. Here is what I tested:
InetAddress addr = InetAddress.getLocalHost();
datagramSocket = new DatagramSocket(SERVER_PORT, addr);
serverPacket = new DatagramPacket(data, MAX_BUFFER_SIZE, addr, CLIENT_PORT);
DatagramSocket clientSocket = new DatagramSocket(CLIENT_PORT, inetAddress);
DatagramPacket packet = new DatagramPacket(data, MAX_BUFFER_SIZE);
packet.setPort(SERVER_PORT);
datagramSocket.send(serverPacket);
clientSocket.receive(packet);
clientSocket.send(packet);
datagramSocket.receive(serverPacket);
As I said data is 64k byte. However above operation is finished in 2 milliseconds! So when I calculate totalPacketSize / elapsedTime result is huge! I think sockets share data on device, never going to router. Do you have suggestions?
By default, windows generates routes that will route packets that are destined to local interfaces to never leave the PC.
The only solution I've ever had to dealing with this is to route to an intermediate address first - see my question here: Win32 sockets - Forcing ip packets to leave physical interfaces when sending to other local interfaces
So here's what you do - create a second IP address assignment on your wireless adapter, create some route table entries to force the packets to hit the wireless router, and then send from one local address to the second local address.
For instance, if my wireless adapter had addresses 192.168.1.100 and 192.168.1.101, and my router was 192.168.1.1, then I'd create the following route in your windows route table:
route add 192.168.1.101 mask 255.255.255.255 192.168.1.1
Then your sender socket should bind() to 192.168.1.100 and send to 192.168.1.101. Your receiver should bind to 192.168.1.101.
Send and receive, and it should go through the network and not the kernel.
When you are done with your test, delete the route:
route delete 192.168.1.101 mask 255.2555.255.255 192.168.1.1
And unassign the extra address.
I know that this method works, because I use it every day, but it can be tricky to get it to work.