TCP File through port 21?

[WarrenW]

Hi,

Is there any way to setup a tcp server on port 21 for a computer that is behind a router and still connect to it? Or will it still be blocked?

How about this http tunneling I've read some about. How does that work? Do you use port 80 and fool the router to think its a web page coming back?

Is there any way to get around the router problems ever? Any tricks?

I know, I ask what everyone else does for - the impossible! :)

Thanks!

[John_420]

Not sure but i think you can open the port manually.

[k1ll3rdr4g0n]

Most ISPs do not block port 21 so you can open up that port on your router. (Its called port forwarding)

[WarrenW]

Thanks, I know all about port forwarding but users of software I write will not. Just trying to find any way around it still for tcp connections between two users directly instead of going through a main server.

[k1ll3rdr4g0n]

Nope, you have to port forward or use a server that is outside both networks (ie a relay server). You can try UPnP, but that's a gamble too because not all routers support it. You can do what all the other corporations do, pay to port forward for them.

[Milad87]

If u are thinking about connecting to another computer behind a router u can use client/server app. with reverse connection

[samtheman]

I am sure port 21 is FTP Not absoltely sure though..

And yes, tunelling is used in p2p clients aswell where everyone is behind a router, you must send a packet and expect a reply to initiate a transfer.

[dbasnett]

TCP Port 21 is FTP Control. Well Known Ports (http://www.iana.org/assignments/port-numbers)

Not a good choice. Read up on P2P

P2P (http://www.hardwaresecrets.com/article/423)

[dbasnett]

And the P2P should lead you to what the real issue is,

NAT Traversal (http://en.wikipedia.org/wiki/NAT_traversal)