detect local server when using a Point-to-Point conenction

[ensonic]

When we are online, check if we can detect a local open roberta server. This would help using p2p-connections like usb/bt. We would e.g. do a mdns discovery on the robot and mdns announcements of local clients.

Ideally we'd just try to connect to :1999. On the machine that hosts the server:

$ ifconfig usb0
usb0      Link encap:Ethernet  HWaddr 12:16:53:48:af:38  
          inet addr:172.16.243.1  Bcast:172.16.243.255  Mask:255.255.255.0
          inet6 addr: fe80::1016:53ff:fe48:af38/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:18 errors:0 dropped:0 overruns:0 frame:0
          TX packets:77 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2917 (2.9 KB)  TX bytes:10592 (10.5 KB)
$ route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.16.243.0    0.0.0.0         255.255.255.0   U     1      0        0 usb0

On the ev3:

$  ifconfig usb0
 usb0      Link encap:Ethernet  HWaddr 02:16:53:48:af:38  
          inet addr:172.16.243.50  Bcast:172.16.243.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST DYNAMIC  MTU:1500  Metric:1
          RX packets:8151 errors:0 dropped:220 overruns:0 frame:0
          TX packets:6056 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2337065 (2.2 MiB)  TX bytes:837457 (817.8 KiB)
$ route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         172.16.243.1    0.0.0.0         UG    0      0        0 usb0
172.16.243.0    0.0.0.0         255.255.255.0   U     0      0        0 usb0
172.16.243.1    0.0.0.0         255.255.255.255 UH    0      0        0 usb0

So we could grab the gateway address for usbX or hciX and try to connect to :1999.

First step would be a local python prototype. If that works, we'd need changes in the UI to support a "discovered server" and changes on this module to run a thread an periodically run the discovery (the code from the previously mentioned prototype).