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  • InetAddress.isReachable() ?

    From =?UTF-8?Q?Arne_Vajh=c3=b8j?=@21:1/5 to Knute Johnson on Fri Oct 23 13:14:36 2020
    On 10/23/2020 12:50 PM, Knute Johnson wrote:
    InetAddress.isReachable() only works if I run Java as root.  Any idea
    how to make it work with a regular user?  The docs say "A typical implementation will use ICMP ECHO REQUESTs if the privilege can be obtained".  I'm assuming that's why it won't work as a regular user.

    Is it worth it?

    The method can return false and the service you want to use
    can be available (firewall blocking ICMP and Echo but not application protocol).

    The method can return true and the service you want to use
    can be unavailable (OS running but server application down).

    I think you would be better of connecting to the service
    you want to use and handle errors there.

    Arne

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Knute Johnson@21:1/5 to All on Fri Oct 23 11:50:54 2020
    InetAddress.isReachable() only works if I run Java as root. Any idea
    how to make it work with a regular user? The docs say "A typical implementation will use ICMP ECHO REQUESTs if the privilege can be
    obtained". I'm assuming that's why it won't work as a regular user.

    Xubuntu 20.04
    OpenJDK 15 - BellSoft

    Thanks!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Knute Johnson@21:1/5 to All on Fri Oct 23 18:10:09 2020
    On 10/23/20 12:14 PM, Arne Vajhøj wrote:
    On 10/23/2020 12:50 PM, Knute Johnson wrote:
    InetAddress.isReachable() only works if I run Java as root.  Any idea
    how to make it work with a regular user?  The docs say "A typical
    implementation will use ICMP ECHO REQUESTs if the privilege can be
    obtained".  I'm assuming that's why it won't work as a regular user.

    Is it worth it?

    Yes

    The method can return false and the service you want to use
    can be available (firewall blocking ICMP and Echo but not application protocol).

    No firewalls there.

    The method can return true and the service you want to use
    can be unavailable (OS running but server application down).

    No service to connect to. Just want to see if there is a path to the
    router.

    I think you would be better of connecting to the service
    you want to use and handle errors there.

    Again no service to connect to.

    It's an internal network and I'm fielding calls all the time that 'we
    aren't getting updates to our data'. If I can ask is the little box
    green or red I'll know with some certainty the status of their network connection. I'm 1600 km from the site so I can't just pop over for a
    look see. I can't ask them to ping the router, that's a step too far.
    The network service at the remote sites is interrupted on a fairly
    regular basis.

    So yes I would really like to figure out how to make this work is it is possible.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Knute Johnson@21:1/5 to All on Fri Oct 23 19:38:34 2020
    On 10/23/2020 19:30, Arne Vajhøj wrote:
    On 10/23/2020 7:10 PM, Knute Johnson wrote:
    On 10/23/20 12:14 PM, Arne Vajhøj wrote:
    On 10/23/2020 12:50 PM, Knute Johnson wrote:
    InetAddress.isReachable() only works if I run Java as root.  Any
    idea how to make it work with a regular user?  The docs say "A
    typical implementation will use ICMP ECHO REQUESTs if the privilege
    can be obtained".  I'm assuming that's why it won't work as a
    regular user.

    Is it worth it?

    Yes

    OK.

    The method can return false and the service you want to use
    can be available (firewall blocking ICMP and Echo but not application
    protocol).

    No firewalls there.

    The method can return true and the service you want to use
    can be unavailable (OS running but server application down).

    No service to connect to.  Just want to see if there is a path to the
    router.

    I think you would be better of connecting to the service
    you want to use and handle errors there.

    Again no service to connect to.

    It's an internal network and I'm fielding calls all the time that 'we
    aren't getting updates to our data'.  If I can ask is the little box
    green or red I'll know with some certainty the status of their network
    connection.  I'm 1600 km from the site so I can't just pop over for a
    look see.  I can't ask them to ping the router, that's a step too far.
    The network service at the remote sites is interrupted on a fairly
    regular basis.

    So yes I would really like to figure out how to make this work is it
    is possible.

    I cannot believe there are any ways to get around the privilege issue.

    If there were then it would be a bug that would be fixed.

    That leaves you with the awful hack of running the external
    ping command and read output.

    Arne


    That's what I was afraid of Arne. Oh well, I didn't have anything else
    to do this week :-).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From =?UTF-8?Q?Arne_Vajh=c3=b8j?=@21:1/5 to Knute Johnson on Fri Oct 23 20:30:51 2020
    On 10/23/2020 7:10 PM, Knute Johnson wrote:
    On 10/23/20 12:14 PM, Arne Vajhøj wrote:
    On 10/23/2020 12:50 PM, Knute Johnson wrote:
    InetAddress.isReachable() only works if I run Java as root.  Any idea
    how to make it work with a regular user?  The docs say "A typical
    implementation will use ICMP ECHO REQUESTs if the privilege can be
    obtained".  I'm assuming that's why it won't work as a regular user.

    Is it worth it?

    Yes

    OK.

    The method can return false and the service you want to use
    can be available (firewall blocking ICMP and Echo but not application
    protocol).

    No firewalls there.

    The method can return true and the service you want to use
    can be unavailable (OS running but server application down).

    No service to connect to.  Just want to see if there is a path to the router.

    I think you would be better of connecting to the service
    you want to use and handle errors there.

    Again no service to connect to.

    It's an internal network and I'm fielding calls all the time that 'we
    aren't getting updates to our data'.  If I can ask is the little box
    green or red I'll know with some certainty the status of their network connection.  I'm 1600 km from the site so I can't just pop over for a
    look see.  I can't ask them to ping the router, that's a step too far.
    The network service at the remote sites is interrupted on a fairly
    regular basis.

    So yes I would really like to figure out how to make this work is it is possible.

    I cannot believe there are any ways to get around the privilege issue.

    If there were then it would be a bug that would be fixed.

    That leaves you with the awful hack of running the external
    ping command and read output.

    Arne

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Gregorie@21:1/5 to Knute Johnson on Sat Oct 24 11:45:33 2020
    On Fri, 23 Oct 2020 19:38:34 -0500, Knute Johnson wrote:

    On 10/23/2020 19:30, Arne Vajhøj wrote:
    On 10/23/2020 7:10 PM, Knute Johnson wrote:
    On 10/23/20 12:14 PM, Arne Vajhøj wrote:
    On 10/23/2020 12:50 PM, Knute Johnson wrote:
    InetAddress.isReachable() only works if I run Java as root.  Any
    idea how to make it work with a regular user?  The docs say "A
    typical implementation will use ICMP ECHO REQUESTs if the privilege
    can be obtained".  I'm assuming that's why it won't work as a
    regular user.

    Is it worth it?

    Yes

    OK.

    The method can return false and the service you want to use can be
    available (firewall blocking ICMP and Echo but not application
    protocol).

    No firewalls there.

    The method can return true and the service you want to use can be
    unavailable (OS running but server application down).

    No service to connect to.  Just want to see if there is a path to the
    router.

    I think you would be better of connecting to the service you want to
    use and handle errors there.

    Again no service to connect to.

    It's an internal network and I'm fielding calls all the time that 'we
    aren't getting updates to our data'.  If I can ask is the little box
    green or red I'll know with some certainty the status of their network
    connection.  I'm 1600 km from the site so I can't just pop over for a
    look see.  I can't ask them to ping the router, that's a step too far.
    The network service at the remote sites is interrupted on a fairly
    regular basis.

    So yes I would really like to figure out how to make this work is it
    is possible.

    I cannot believe there are any ways to get around the privilege issue.

    If there were then it would be a bug that would be fixed.

    That leaves you with the awful hack of running the external ping
    command and read output.

    Arne


    That's what I was afraid of Arne. Oh well, I didn't have anything else
    to do this week :-).

    Apologies if this is stuff you already know, but I tend to use
    traceroute, wireshark and nmap to sort out network problems and this
    sounds as if it might be some sort of network problem.

    Could it be a physical problem, e.g. rodent or physical cable damage
    causing an intermittent connection?

    traceroute can show which switch or device is the last device accessible
    along the message route.

    Wireshark can be used to show what is being transferred and what
    responses are returned when a problem occurs.

    nmap would seem less useful in this case, though at least it shows what
    ports are open at the destination IP address, so can spot firewall
    problems and dodgy interface cards.


    --
    --
    Martin | martin at
    Gregorie | gregorie dot org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Knute Johnson@21:1/5 to Martin Gregorie on Thu Oct 29 15:23:51 2020
    Sorry to be slow responding Martin. It's been one of those weeks.

    The basic setup is this; we have a server sending Multicast data
    packets through a VPN over the internet. The end points have user
    programs that use this data for some presentations. We are tasked with supporting the system but large parts of it are beyond our control. The
    main issue for us is the remote locations ISP reliability. I wanted a
    simple way to tell on the first phone call whether there was a network
    path to the server without having to log into the VPN network. The
    software running on the remote locations has indications that data has
    not arrived recently but it has no indication of quality. When they
    call and tell me the system is showing old data I can ask if the box is
    red or green and start trouble shooting from there. These folks are not
    up to running nmap or wireshark or anything for that matter. Using a
    Process to run ping seems to work fine, just more code that I wanted to
    write. Since Windows and Linux use a different set of options for ping
    I had to detect the OS and change the accordingly.

    I'm not sure why Java has the privilege issue with
    InetAddress.isReachable() but it does.

    knute...


    On 10/24/2020 06:45, Martin Gregorie wrote:
    On Fri, 23 Oct 2020 19:38:34 -0500, Knute Johnson wrote:

    On 10/23/2020 19:30, Arne Vajhøj wrote:
    On 10/23/2020 7:10 PM, Knute Johnson wrote:
    On 10/23/20 12:14 PM, Arne Vajhøj wrote:
    On 10/23/2020 12:50 PM, Knute Johnson wrote:
    InetAddress.isReachable() only works if I run Java as root.  Any
    idea how to make it work with a regular user?  The docs say "A
    typical implementation will use ICMP ECHO REQUESTs if the privilege >>>>>> can be obtained".  I'm assuming that's why it won't work as a
    regular user.

    Is it worth it?

    Yes

    OK.

    The method can return false and the service you want to use can be
    available (firewall blocking ICMP and Echo but not application
    protocol).

    No firewalls there.

    The method can return true and the service you want to use can be
    unavailable (OS running but server application down).

    No service to connect to.  Just want to see if there is a path to the >>>> router.

    I think you would be better of connecting to the service you want to >>>>> use and handle errors there.

    Again no service to connect to.

    It's an internal network and I'm fielding calls all the time that 'we
    aren't getting updates to our data'.  If I can ask is the little box
    green or red I'll know with some certainty the status of their network >>>> connection.  I'm 1600 km from the site so I can't just pop over for a >>>> look see.  I can't ask them to ping the router, that's a step too far. >>>> The network service at the remote sites is interrupted on a fairly
    regular basis.

    So yes I would really like to figure out how to make this work is it
    is possible.

    I cannot believe there are any ways to get around the privilege issue.

    If there were then it would be a bug that would be fixed.

    That leaves you with the awful hack of running the external ping
    command and read output.

    Arne


    That's what I was afraid of Arne. Oh well, I didn't have anything else
    to do this week :-).

    Apologies if this is stuff you already know, but I tend to use
    traceroute, wireshark and nmap to sort out network problems and this
    sounds as if it might be some sort of network problem.

    Could it be a physical problem, e.g. rodent or physical cable damage
    causing an intermittent connection?

    traceroute can show which switch or device is the last device accessible along the message route.

    Wireshark can be used to show what is being transferred and what
    responses are returned when a problem occurs.

    nmap would seem less useful in this case, though at least it shows what
    ports are open at the destination IP address, so can spot firewall
    problems and dodgy interface cards.



    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Gregorie@21:1/5 to Knute Johnson on Thu Oct 29 21:36:03 2020
    On Thu, 29 Oct 2020 15:23:51 -0500, Knute Johnson wrote:

    Sorry to be slow responding Martin. It's been one of those weeks.

    No problem - been there too. Thanks for the fuller explanation.

    Of course you can't ask a client to run Wireshark, but it probably
    wouldn't help with the problem anyway, now that I understand the setup.

    However, if you know the problem client's URL or IP or can get then to
    tell you what it is, then there's nothing to stop you pinging them or
    using traceroute to see if the problem was transient or permanent and
    where it is.

    Whether you get a response from ping will depend on how their cable/ADSL/ whatever modem and firewall is configured. Mine, for example, is
    configured to give no response whatsoever on any channel to stop the bad
    lads from thinking there's anything turned on at my site (and checked for invisibility against Gibson Labs).

    However, traceroute should do its thing no matter what state how the
    client 's front door is configured. because it will and either reach the client's endpoint and say so, or, if it can't reach that, show you where
    the failure is.

    I hope this is useful info.


    --
    --
    Martin | martin at
    Gregorie | gregorie dot org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From =?UTF-8?Q?Arne_Vajh=c3=b8j?=@21:1/5 to Knute Johnson on Thu Oct 29 21:47:12 2020
    On 10/29/2020 4:23 PM, Knute Johnson wrote:
    I'm not sure why Java has the privilege issue with
    InetAddress.isReachable() but it does.

    Someone thought that use of ICMP in Linux should
    require privs.

    The ping executable is rws while the java
    executable is rwx.

    Arne

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Knute Johnson@21:1/5 to All on Sun Nov 1 10:30:52 2020
    On 10/29/20 8:47 PM, Arne Vajhøj wrote:
    On 10/29/2020 4:23 PM, Knute Johnson wrote:
    I'm not sure why Java has the privilege issue with
    InetAddress.isReachable() but it does.

    Someone thought that use of ICMP in Linux should
    require privs.

    The ping executable is rws while the java
    executable is rwx.

    Arne



    OK, so that got me curious and I checked on my Xubuntu box that I was
    using when writing this program and found this:

    /usr/bin$ ls -al ping
    -rwxr-xr-x 1 root root 72776 Jan 30 2020 ping

    But then for fun I looked on my RaspberryPi and found:

    ~ $ ls -al /bin/ping
    -rwsr-xr-x 1 root root 55720 Jan 13 2020 /bin/ping

    The Buntus are usually fairly lax in some of their settings but I
    thought this was interesting. Useless but interesting.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)