Remark: The test using the public IP is not conclusive since normally one cannot self-connect through the router.

It might be worthwhile testing another computer at your home with a first-time installation of java and Minecraft.

Question: Is your Minecraft server in the same country as you ? It might be useful to test with different countries, or using Pingtest.net.

I'm suggesting this because I suspect the Minecraft client (or even Java) of badly handling lags with a premature timeout and with no attempt to reconnect.

In the meantime, the Auto-Reconnect plugin might simplify quickly getting over the error.

Remark: The test using the public IP is not conclusive since normally one cannot self-connect through the router.

It might be worthwhile testing another computer at your home with a first-time installation of java and Minecraft.

Question: Is your Minecraft server in the same country as you ? It might be useful to test with different countries, or using Pingtest.net.

I'm suggesting this because I suspect the Minecraft client (or even Java) of badly handling lags, doing a premature timeout and then making no attempt to reconnect.

In the meantime, the Auto-Reconnect plugin might simplify quickly getting over the error.

A good test to find if the lag problem is caused by an installed product, is to boot into Safe Mode with Network (if the generic display is acceptable with Minecraft). In this mode, no non-Microsoft product can cause lag problems.

The most frequent kind of problematic products that can introduce lags are security suites or parental control products. In the case of the poster, the culprit was K9.