Ping uses ICMP which operates directly above IP, not using TCP and UDP and hence has no notion of ports. Traceroute purposely sends to an unused UDP port range, and waits for an ICMP with TTL exceed or port unreachable. Neither tool helps directly determine which ports are available on a host
The routers also in general don't look at ports and anyway won't be listening to the ports you have in mind. (unless the router has an Access COntrol List or other packet filter looking particular ports, it will pass the IP packet provided it has a route). If you try to send a packet that is blocked by the router because of an ACL, a router may either silent drop the packet or send a ICMP port unreachable message back. (Your application will normally report this). Hence you may or may not be able to determine where the issue lies. You can test TCP reachability by "telnet host port" and check whether you get "connection refused", or an ICMP message back. UDP protocols are usually silently dropped by hosts is they are not listening on that port. The normal network assumptions is that ICMP will only test IP routing tables and links, it doesn't prove that your applications can get through. (Of course if ICMP is blocked by the router/host you cannot be sure that your application will or won't get through) No easy solution I'm afraid Martin Visser Network Consultant - Compaq Global Services Compaq Computer Australia 3 Richardson Place North Ryde, Sydney NSW 2113 Australia Phone: +61-2-9022-1670 Mobile: +61-411-254-513 Email:[EMAIL PROTECTED] -----Original Message----- From: The Pimply Faced Youth [mailto:[EMAIL PROTECTED]] Sent: Wednesday, 13 March 2002 1:15 PM To: [EMAIL PROTECTED] Subject: [SLUG] pinging a port number. Is it possible to either ping or traceroute over a specific port number? If so, how can I determine the break in connection? -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://lists.slug.org.au/listinfo/slug -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://lists.slug.org.au/listinfo/slug
