What network port to use for mobile app -

i have mobile app uses socket connection communicate server. however, seems users complaining port blocked isp, or wireless network.

is there range of ports are well-known enough not blocked not used mobile devices use? or there better way address issue?

asking isp/wireless network admin unblock port not feasible thing me do.

edit: i'm looking @ canadian, us, , european mobile operators in particular.

the best , port use 80 standard http traffic.

you try... 443 ssl http traffic 8080 backup http traffic port used proxy servers or links.

but if remotely worried networks blocking traffic standard http , port 80 ways go. networks allow port 80 if allow thing.

btw times way ask isps/networks open port server isn't ideal if block port 80 going have ask them.