How to check if ports are blocked?

Is there any way I can check which ports are being blocked by an ISP,
on say a broadband connection?

Obviously if Port 443 is blocked then any HPPTS sites won't work...
etc.

Peter wrote:
> Is there any way I can check which ports are being blocked by an ISP,
> on say a broadband connection?

'telnet hostnameorIP portnumber' tries to make a connection, its value
depends on what response the other end will give to a telnet session on
that port. The error messages / speed of response may give you a clue
if the outbound connection is refused.

Inbound the port scanners like ShieldsUp from GRC or
http://www.netmonitor.org/tools/nscan.php should help the other way,
providing you have a port open and listening and no firewall issues.

Phil

"PhilT" <(E-Mail Removed)> wrote

>
>Peter wrote:
>> Is there any way I can check which ports are being blocked by an ISP,
>> on say a broadband connection?
>
>'telnet hostnameorIP portnumber' tries to make a connection, its value
>depends on what response the other end will give to a telnet session on
>that port. The error messages / speed of response may give you a clue
>if the outbound connection is refused.
>
>Inbound the port scanners like ShieldsUp from GRC or
>http://www.netmonitor.org/tools/nscan.php should help the other way,
>providing you have a port open and listening and no firewall issues.
>
>Phil

That's the problem - normally one needs to have an application
program, or an operating system function, servicing packets on the
port before one is going to get any response from it.

The question should have been: is there is a website which is running
some application that replies on *all* ports, so one could do an
outbound port check.

Most servers will not respond at all to any port other than those
specifically open (e.g. 80) so they are of no use for checking this.

Peter wrote:
> Is there any way I can check which ports are being blocked by an ISP,
> on say a broadband connection?
>
> Obviously if Port 443 is blocked then any HPPTS sites won't work...
> etc.

Ask the ISP.

Paul Cupis <(E-Mail Removed)> wrote

>Peter wrote:
>> Is there any way I can check which ports are being blocked by an ISP,
>> on say a broadband connection?
>>
>> Obviously if Port 443 is blocked then any HPPTS sites won't work...
>> etc.
>
>Ask the ISP.

HOHOHO. Have you tried asking the NMWG (National Minimum Wage Gorilla)
at your average ISP, or better still a GSM network provider, this sort
of Q?

On Sat, 28 Oct 2006 11:47:15 +0100, Peter
<occassionally-(E-Mail Removed)> wrote:

>The question should have been: is there is a website which is running
>some application that replies on *all* ports, so one could do an
>outbound port check.
>
>Most servers will not respond at all to any port other than those
>specifically open (e.g. 80) so they are of no use for checking this.

Do an nmap scan on a friend who has a firewall/NAT up? If your ISP is
blocking a port it will show as closed I'd have thought? Can't see any
reason why they wouldn't send a closed response to a connect?

In essence find a friend who believes in all this "stealth" shit - ie
they have a firewall/router/whatever that doesn't respond to
unsolicited incoming traffic. Then look for the instances where a port
is shown as closed - that'll be your ISP (or theirs). If you can run
another nmap scan to the same friend from a different connection then
that'd help too.

Process of elimination really :-(
--
John Naismith

Peter wrote:
> Paul Cupis <(E-Mail Removed)> wrote
>
>> Peter wrote:
>>> Is there any way I can check which ports are being blocked by an ISP,
>>> on say a broadband connection?
>>>
>>> Obviously if Port 443 is blocked then any HPPTS sites won't work...
>>> etc.
>> Ask the ISP.
>
> HOHOHO. Have you tried asking the NMWG (National Minimum Wage Gorilla)
> at your average ISP, or better still a GSM network provider, this sort
> of Q?

Then don't ask them. Ask second/third line support, email your request,
read the ISPs website etc

Paul Cupis wrote:
> Peter wrote:
>> Paul Cupis <(E-Mail Removed)> wrote
>>
>>> Peter wrote:
>>>> Is there any way I can check which ports are being blocked by an
>>>> ISP, on say a broadband connection?
>>>>
>>>> Obviously if Port 443 is blocked then any HPPTS sites won't work...
>>>> etc.
>>> Ask the ISP.
>>
>> HOHOHO. Have you tried asking the NMWG (National Minimum Wage
>> Gorilla) at your average ISP, or better still a GSM network
>> provider, this sort of Q?
>
> Then don't ask them. Ask second/third line support, email your
> request, read the ISPs website etc

https://www.grc.com/x/ne.dll?bh0bkyd2

has a checker and information to help. Think it answers your question
although it is more about sheilding and stealth of ports.

Mark BR

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"John Naismith" <(E-Mail Removed)> ha scritto nel messaggio
news:(E-Mail Removed)...
> On Sat, 28 Oct 2006 11:47:15 +0100, Peter
> <occassionally-(E-Mail Removed)> wrote:
>
> >The question should have been: is there is a website which is running
> >some application that replies on *all* ports, so one could do an
> >outbound port check.
> >
> >Most servers will not respond at all to any port other than those
> >specifically open (e.g. 80) so they are of no use for checking this.
>
> Do an nmap scan on a friend who has a firewall/NAT up? If your ISP is
> blocking a port it will show as closed I'd have thought? Can't see any
> reason why they wouldn't send a closed response to a connect?
>
> In essence find a friend who believes in all this "stealth" shit - ie
> they have a firewall/router/whatever that doesn't respond to
> unsolicited incoming traffic. Then look for the instances where a port
> is shown as closed - that'll be your ISP (or theirs). If you can run
> another nmap scan to the same friend from a different connection then
> that'd help too.
>
> Process of elimination really :-(
> --
> John Naismith