Forums Connection Issues Ackward Error

I came across a really strange problem recently and i can't seem to figure out what causes it. I've been DCC'ing to a friend of mine on regularly basis and we never had any problems until recently. This is the current situation :

When I sent a file from my computer ( Side A ) to his, he can accept and the file transfer completes with no problems.
But when he tries to sent a file from his computer ( Side B ) towards me the accept window pops up but after accepting the all familiar 'Unable to connect' error shows it self.

So he double checks his settings and ports and reports back that everything is in working order. Nothing has changed the last 6 months, so the question rises why doesn't it work.

So i go check the log of my own router and find the following :

FIREWALL icmp check (1 of 1): Protocol: ICMP Src ip: xx.xxx.xxx.143 (Side B) Dst ip: xxx.xx.xxx.150 (Side A) Type: Destination Unreachable Code: Communication Administratively Prohibited

Side A:
mIRC v6.32 Khaled Mardam-Bey
Connected through router, ports forwarded correctly. ( Confirmed receive & sent on same network with other mIRC users. )
Side B:
mIRC v6.12 Khaled Mardam-Bey ( Old version cause he doesn't like the new version or something )
Connected through router, ports forwarded correctly. ( Confirmed receive & sent on same network with other mIRC users. )

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So my question is, why does my router block the DCC transfers which he is sending to me while it lets others through without any problem. Have been on Google to try to figure this out but the only results I found there are :
- Communication administratively prohibited. The network administrator has blocked trace route at this router. What sort of means : Destination Unreachable.
- Some stuff about IP tables and unix
- Some logs about hackers trying to hack into a honeynet

So not really anything which is of any help to me, and that is why I turn to you people. In the hope that anyone can point me in the right direction or explain to me what goes wrong or how to fix this problem for my friend.

Thanks in advance

First of all you should realize that it's the *sender* that needs to forward ports on their router, because the receiver is the one making the outgoing connection.. Routers pretty much never block outgoing connections (unless you're connected to some school/office/highly secured network), so it's rarely the receiver's fault.

When your friend sends you a file, you connect to them, meaning if anything is blocking the connection it's his router, not yours. You shouldn't have to fiddle with anything on your end.

Can he dcc send to anybody else? Has his local ip changed recently? If he's on DHCP this is highly possible. This would affect port forwarding. I'll bet good money that something did in fact change in his network that broke his port forwarding configuration.

He can DCC normally to other people, it just that when he dcc's to me my router gives the following error :

Destination Unreachable Code: Communication Administratively Prohibited

So its working normally for him and for me, its just when he tries to sent to me my router blocks it while it lets other connections true.