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CanYouSeeMe is good for checking if a system can be connected to by external systems on the Internet, but is there a way to see if the system can be pinged?

For example, my ISP seems to be blocking every port such that CanYouSeeMe (or any other system) cannot connect to my system regardless of the port—eg, FTP, Telnet, HTTP, MySQL, SVN, etc. (Yes, I am certain that the router/firewall is not the offender.) That is, I can connect via localhost or NAT IP, but not public IP. That said, I can successfully ping my public IP. However the response times are identical to those from pinging my NAT IP and localhost, so I’m not sure that I am indeed pinging my public IP (ie, is it being automatically redirected to localhost?) Therefore, I am trying to find a way/service that can try pinging my system to see if my system is visible to the outside world at all. CanYouSeeMe is good for the most part, but it is too limited (no protocol options, so I can’t test UDP or ICMP, therefore no ping).

Does anyone know of a more comprehensive way to test for the existence of a system?

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    You sure it is your ISP that blocks all the ports and not the settings on your router and/or firewall?
    – Greg
    Jun 23, 2011 at 17:10
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    Yup.​​​​​​​​​​​
    – Synetech
    Jun 23, 2011 at 18:35

1 Answer 1

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Here are a couple of online tools that provide "ping" and "port check" (to check if a specific TCP port responds to connection attempts) and a variety of other related tools:

These sites have links to numerous other (mostly regional) sites like the above ones:

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  • Yup, that did the trick. The traceroute shows that it dies once it hits the ISP. The ping failed altogether which implies that the local ping automatically redirects the public IP to localhost. Strange.
    – Synetech
    Jun 23, 2011 at 18:37
  • When your router gets instructions to route to a specific IP address, if it's local it may be routing back locally and not bothering with the internet at all (many home routers function this way). That could explain why you can ping it locally (resolution of name-to-ip-address is an entirely different process than sending ICMP traffic, which is what the "ping" utility uses).
    – Randolf Richardson
    Jun 23, 2011 at 23:03
  • Regarding redirection, ICMP is not necessarily a useful gauge for this because many administrators do block ICMP traffic while letting other traffic through. That's why the "port check" utility is so useful -- you can use it to determine if TCP traffic gets through where ICMP traffic doesn't. Unfortunately that tool doesn't have an option to test UDP traffic, but in most cases I find that UDP is fine where TCP works.
    – Randolf Richardson
    Jun 23, 2011 at 23:05
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    Keep in mind that some ISPs violate the RFCs and block pings to help stop DOS attacks.
    – Hydaral
    Jul 14, 2011 at 2:38
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    @Randolf Richardson, I agree, it is terrible, and have personally found it to be quite rare. It's the poor man's solution to DOS.
    – Hydaral
    Jul 14, 2011 at 6:00

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