I can't connect to my firends server

[Midgar]

Hi there .

I've recently started playing HL deathmatch with my friend but we've got a problem.

Whenever we try to create a server we can't connect to each. I click the link that says join game but it just says "the server does not respond".

However we can both connect to other interent servers.

Can anyone help please?

[Xendance]

Either

a) you must type "sv_lan 0" in the console
b) you must port forward
c) you must turn your firewall off