Problem with recieving data from socket after losing WiFi network

Question

Hello,

I have client/server application. Client on iPhone, server on Windows based machine. First, i establish connection to my server and that is works fine. When I go away from WiFi area - client disconnects (is's expected). But, when I enter into WiFi area again and tried connect to server, connection is established but client doesn't recieve any data. I need restart my client application to connect to server. Why it is happens? This happens always when I'm sending data in both direction with about 1 Mbit/s.

I'll be thankful for any idea =)

Thanks

Answer 1

When you leave the Wifi area, Tcp detects that you have no connection, so the server will drop the Tcp connection. You have to reestablish it when you get back in Wifi range.

I am not an expert in this area, but maybe there is a time limit, within which, if you reenter the Wifi, the existing Tcp connection is reused?

However, to be robust, you should always code your app to retry, if operating in Wifi is one of your main scenarios.

Answer 2

Your TCP has gone into a long timeout trying to get the data through on a link that doesn't exist for a while. You need to detect this happening, close the socket, and reconnect.

Or, switch to using UDP if you don't actually need TCP's reliability (although this isn't its proper name, think of UDP as the 'Unreliable Datagram Protocol', in other words there's no guarantee of delivery, nor of delivery in the correct order).