[General] - Can't connect to a public server on the same LAN - server not responding

[myxal]

Bug Submission:

Category: General

Issue Title: Can't connect to a public server on the same LAN - server not responding

Issue Description: Hi there, this is the setup:

[*] The dedicated server is a small linux box which sits directly connected to the internet and also provides NAT to the home network - ie. it has 2 interfaces, WAN and LAN (192.168.1.1)

[*] The client is an OS X machine, sitting behind NAT provided by the server. (192.168.1.136)

A friend on his own internet connection has no problems connecting to my server. I see logs on the server that he is connecting, leaving, etc.

When I try to connect, there are no logs on the server console.

tcpdump executed on the mac reveals this (public IP replaced with XXXs):

$ tcpdump -nqr /tmp/dst.pcap

reading from PCAP-NG file /tmp/dst.pcap

21:31:08.250413 IP 192.168.1.136.59249 > XXX.XXX.XXX.XXX.10999: UDP, length 1172

21:31:08.250997 IP 192.168.1.1.10999 > 192.168.1.136.59249: UDP, length 28

21:31:10.251392 IP 192.168.1.136.59249 > XXX.XXX.XXX.XXX.10999: UDP, length 1172

21:31:10.251996 IP 192.168.1.1.10999 > 192.168.1.136.59249: UDP, length 28

21:31:12.251634 IP 192.168.1.136.59249 > XXX.XXX.XXX.XXX.10999: UDP, length 548

21:31:12.252170 IP 192.168.1.1.10999 > 192.168.1.136.59249: UDP, length 28

21:31:14.256761 IP 192.168.1.136.59249 > XXX.XXX.XXX.XXX.10999: UDP, length 548

21:31:14.257300 IP 192.168.1.1.10999 > 192.168.1.136.59249: UDP, length 28

21:31:16.263895 IP 192.168.1.136.59249 > XXX.XXX.XXX.XXX.10999: UDP, length 548

21:31:16.264472 IP 192.168.1.1.10999 > 192.168.1.136.59249: UDP, length 28

My guess (considering the 2-second intervals and repeating packet sizes) is that the client opens a "socket" to the public IP, then ignores/doesn't receive the responses, which are coming from the internal LAN's IP.

Steps to Reproduce: 1. Run a public dedicated server on the same network as the client, right on the gateway.

2. Try to connect to the server from a Mac client.

Problem: Client claims the server is not responding.