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network-knowledge-base/port_forwarding.md

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+# Port Forwarding how to
+
+You want to open something on your network to the world.
+
+# What is a port
+
+A number between 0 - 65,535 that gets assigned to any application that wants
+to communicate over the network. This number is then added to every packet
+that is transmitted by that application. The system knows that any respone
+packets marked by that port number are to be send to that one application.
+
+This solved the problem on how to make many applications communicate over
+the network simultaneously.
+
+# How firewall works
+
+* Firewall allows outgoing communication on any port.
+* But the incoming traffic gets dropped on all ports, unless it is a response 
+to communication initialized from the inside.
+
+So when you visit a website you initialized communication, you send requests
+to some address an web browser is listening for a response at some port.
+
+# What is port forwarding
+
+What if you want to host something, lets say a minecraft server.<br>
+You set it all up, you have your IP address known to others and they try to connect,
+but your firewall blocks them. Its a connection initialized from the outside.
+
+So you need to tell your router/firewall what to do when traffic comes to
+minecraft default port - `25565`. It should be send to some IP address
+on your local LAN where your minecraft server is running.