Please explain to me - Ethernet & Weather Underground

I like to connect to Weather Underground Server.
I try to understand each line of the sketch - from examples etc.

byte mac[] = { 
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};  
// assign an IP address for the controller:
//IPAddress ip(192,168,1,20);
//IPAddress gateway(192,168,1,1); 
//IPAddress subnet(255, 255, 255, 0);
EthernetClient client;
unsigned int localPort = 8888;

byte mac I have from ethernet shield manufacturer website.
I understand that I have to assign IPAddress - in this case, it is 192,168,1,20
Can I assign any?
I'm not sure where to find gateway and subnet addresses.
From my router, I can get:
WAN - IP Address, Subnet Mas, Default Gateway, Primary and Secondary DNS Server
LAN - Mac Address, IP and Subnet Mask

I understand that I have to have
Mac address and IPAdress.
But do I need Gateway and Subnet addresses - if yes where to find them

What exactly is unsigned int localPort = 8888

Thx in advance