Avoid MarkMods patch... It brings more trouble than it solves.
First, ensure you are able to contact the other machine on your LAN.
As Ed suggested, you may try to ping (careful of the firewall).
Before doing that, check that both machines are on the same (sub)network:
- Start Menu > Execute > Type 'cmd' > Click OK
or Start Menu > All programs > Accessories > Command Prompt
- Type 'ipconfig'
- In the list, find the network interface you are using to connect to the network
- Compare with the other machine that IP addresses/subnet are compatible and not conflicting
==========
To host a server in SWAT 4, the hosting machine must be able to
receive UDP traffic on ports 10480-10483 and be able to
send TCP or UDP traffic on any port.
By default, Windows Firewall does not block outgoing traffic so there is nothing to worry on that point.
To allow SWAT 4 Dedicated Server traffic, you have 2 options:
- The simplest, allow the dedicated server binary (Swat4DedicatedServer.exe) in the firewall
- More advanced, open specific protocol/ports (UDP, 10480 to 10483) for incoming traffic in the advanced panel of the Windows firewall
[EDIT]
I think I found out the problem striking you:
Read the III. Troubleshooting section of TTF post (stuff copy-pasted from the Web; you can find it in several places)