[SOLVED] Difficulty With Minecraft Server

This is yet another "cant' set up a Minecraft server" post ... Hoping that Minecraft Servers List will be capable of helping. The short version is that the server runs on my computer, but not on his.

Our computers are connected via ethernet cable directly to the ASUS RT–AC86U router. His local IP address is 192.168.50.166.

These are the settings for port forwarding:

Service Name Minecraft Source IP (blank). Port Range: 2565 Local IP: 192.168.50.166 Port: 25565 TCP : BOTH

He connects to 192.168.50.166 when he is running Minecraft on his personal computer. If you enter an external IP (obtained through the "Network Map" page in the router settings) it will return the error message:

Failed to connect to the server io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection timed out: no further information

If I try to connect from my computer to 192.168.50.166 I get exactly the same error from Minecraft.

Here's the real kicker: If I run the server on my computer (192.168.50.48) and change the Local IP port forward settings accordingly, EVERYTHING WORKS. I can connect to the Minecraft server using either my local IP, or the external IP.