General TCP protocol communication question

[msrohman]

If a (PC) client sends a TCP SYN packet to a system using a destination TCP port 80..and that system is not listening on TCP port 80..does the system respond with some sort of TCP packet?

Thanks,

Mike

[a.kiprawih]

Hi,

If tcp 80 is not opened, the system will not give any respond or acknowledge the syn request.

Rgds,

AK

[hemendoz]

Hmmm....what about ICMP port unreachable??? :)

[mhellman]

You should try it yourself using tcpdump or ethereal or whatever to capture the traffic. Different operating systems may behave differently. I believe the typical behaviour is to return a TCP rst...so the answer is yes.

[hemendoz]

Looks like Windows responds with RST-ACK.

Hope that helps!