External Connections

External Connections is the bi-directional way aMule has to communicate with external utilities, like the aMuleWeb and aMuleCMD. So, when a user is controlling aMule remotely, it is sending the commands through the External Conections port and aMule is reading them there (when controlling through a web browser, what is really happening is that aMuleWeb is getting the actions, interpreting them and sending the commands to the External Connection ports).

If both aMule and their utilities run on the same machine, there's no need to redirect the External Connections port in a Firewalled environment (NAT network with a router, etc...). If you had to connect to the External Connections port from somewhere out the network, it would be necessary to configure the router/Firewall/etc properly to accept connections through the External Connection port (this would happen, for example, connecting through aMuleCMD from somewhere outside the network).

NOTE: There are alternate ways of communicating with aMule although External Connections is the only bi-directional way.
Other ways would be the Online Signature (outgoing direction) and ED2KLinks file (ingoing direction).