Hi
Looks like I were right, I finally had some time to spare and went on IRC and got a hold of a friend and started fiddling around, the TCP Three-way handshake weren’t possible, only partial of it was being done.
Here is the packet captures;
Internet >> PC = TCP SYN
PC >> Internet = TCP ACK / SYN
PC >> Internet = TCP ACK / SYN
Internet >> PC = TCP SYN
PC >> Internet = TCP ACK / SYN
PC >> Internet = TCP ACK / SYN
PC >> Internet = TCP ACK / SYN
Internet >> PC = TCP SYN
PC >> Internet = TCP ACK / SYN
You see the final step isn’t being made? And mIRC cycles the process; now take a look at how it should be.
Internet >> PC = TCP SYN
PC >> Internet = TCP ACK / SYN
Internet >> PC = TCP ACK
The above is an actual TCP connection establishment.
What is at fault would be considered my D-Link Router for some abnormal reason, however I’m not getting over the fact that mIRC File Transfers Only seems to be affected, where-else running web-server for instance, TCP initiating connections from remote systems can be made to my web service no problem.
Now I hope you guys will learn something from this, mIRC File Transfer issues doesn’t only correspond with use of software firewall that improperly configured, or Router with filtering capabilities activated. Don’t be so quick to make assumptions, to answer and be done with someone’s problem.
I just wish I could figure out why only mIRC File Transfers are affected….