Under these conditions, connecting via the internet would be superior to direct wi-fi connection. Set up the connection using your server's internet IPD address. If you don't have an internet connection for the server, then each wifi device will have its own address and you will have to connect using that one.
Use the button Local Network Hosts for this.
The thing is FM is saved on a Mac that is not the server, we have a server here but the file is not on the server. Can you give me more information on how to connect via internet? It is shared on the network but the iTouch won't connect to the file when it is not on the same router, even though I have internet connection.
Are you using a local IP address or external IP Address? On your Mac, launch a browser and go to "whatismyip.com". This will give you the machine IP address. Then, in FileMaker Go, try accessing the file via the IP Address.