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Help, connecting to remote device on different network.



  • I've taken the laptop I've been using on my home network away with me, where I away this week the laptop connects to the WiFi network, ifconfig:

      wlan0     Link encap:Ethernet  HWaddr b8:ee:65:dc:70:48  
      inet addr:10.36.38.108  Bcast:10.36.39.255  Mask:255.255.252.0
      inet6 addr: fe80::baee:65ff:fedc:7048/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:6029 errors:0 dropped:0 overruns:0 frame:0
      TX packets:4220 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:3531626 (3.5 MB)  TX bytes:700392 (700.3 KB)
    

    I've got a serial link to the remote device and have run ifconfig on it:

      wlan0     Link encap:Ethernet  HWaddr 44:39:C4:9E:05:58  
      inet addr:10.36.37.136  Bcast:0.0.0.0  Mask:255.255.252.0
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:11323 errors:0 dropped:7870 overruns:0 frame:0
      TX packets:73 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:2177617 (2.0 MiB)  TX bytes:10406 (10.1 KiB)
    

    The laptop cannot ping the remote device and the remote device cannot ping the laptop, can anyone help me to resolve this issue?



  • Solved!

    I enabled the hotspot on my iPhone then connected both the laptop and the remote device via my hotspot.


  • Moderators

    @SPlatten
    even though this question is not related to Qt but rather network management, here is the answer:
    your 2 ip addresses are in a different subnet and thus cannot see each other. See any online subnet mask calculator on the web for reference.



  • Thank you, I need to resolve this so I can continue with development and debugging of the project which is done using Qt Creator.

    The problem is that the network the laptop and hand held device are on, I have no control over the network, the devices get the IP via DHCP.


  • Moderators

    @SPlatten
    As i said. They will never see each other. Unless you change the subnet mask or their ip addresses.

    They both receive their ip addresses from the same DHCP server?!?



  • @raven-worx , as far as I am aware yes, the same server.


  • Lifetime Qt Champion

    @raven-worx

    your 2 ip addresses are in a different subnet and thus cannot see each other.

    I have to disagree here. The network mask is /22 and therefore both devices are in the same subnet.

    See here for complete calculation: http://jodies.de/ipcalc?host=10.36.38.108&mask1=22&mask2=255.255.252.0

    That also shows, that the laptop has the correct broadast address, however, the remote device has not. Not sure if that is part of the issue.

    @SPlatten:

    The laptop cannot ping the remote device and the remote device cannot ping the laptop

    Can you ping anything else known in the network? Can you show the output of route for both systems?

    Regards



  • Running route on the laptop:

    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    default         10.36.36.1      0.0.0.0         UG    0      0        0 wlan0
    10.36.36.0      *               255.255.252.0   U     9      0        0 wlan0
    

    Running route on remote device:

    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    10.36.36.0      *               255.255.252.0   U     0      0        0 wlan0
    default         10.36.36.1      0.0.0.0         UG    0      0        0 wlan0


  • Solved!

    I enabled the hotspot on my iPhone then connected both the laptop and the remote device via my hotspot.


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