No connection when connecting through USB developer mode

[R1tschY]

When phone is connected by USB to computer through developer mode then no connection is possible.

See https://openrepos.net/comment/26268#comment-26268

[dimpflmoser]

Just messed around with kdeconnect / sailfishconnect over usb and got a bit further:
<edit>I think it's not a firewall issue, so please ignore that firewall stuff </edit>
First of all I realised that the Sailfish firewall blocks all incumming connections but ssh on the usb interface. I modified a line in /etc/connman/firewall.conf from:

IPv4.INPUT.RULES = -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT;  -i lo -j ACCEPT

to:

IPv4.INPUT.RULES = -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT; -i rndis0 -j ACCEPT; -i lo -j ACCEPT

This allows all incoming IPv4 traffic via USB interface. I don't think it's too much of a risk.
The connection still didn't work. I stopped sailfish connect and setup netcat / nc to listen to the kdeconnect ports (tcp and udp) and connected the phone via wifi.

Now I got a udp message such as:

{"body":{"deviceId":"_????????_?????_????_????_????????????_","deviceName":"???????","deviceType":"desktop","incomingCapabilities":["kdeconnect.notification.request","kdeconnect.sftp","kdeconnect.runcommand.request","kdeconnect.mpris.request","kdeconnect.telephony","kdeconnect.mousepad.keyboardstate","kdeconnect.mousepad.echo","kdeconnect.clipboard","kdeconnect.battery","kdeconnect.ping","kdeconnect.share.request","kdeconnect.mousepad.request","kdeconnect.notification"],"outgoingCapabilities":["kdeconnect.notification.reply","kdeconnect.notification.request","kdeconnect.sms.request","kdeconnect.telephony.request","kdeconnect.mpris","kdeconnect.battery.request","kdeconnect.clipboard","kdeconnect.sftp.request","kdeconnect.ping","kdeconnect.share.request","kdeconnect.runcommand","kdeconnect.notification","kdeconnect.mousepad.request","kdeconnect.findmyphone.request"],"protocolVersion":7,"tcpPort":1716},"id":"????????","payloadSize":0,"payloadTransferInfo":{},"type":"kdeconnect.identity"}

I copied that message, turned off wifi, connected the phone via USB and started sailfish connect.
Still no success.
Then I set up a UDP connection with netcat from the PC to the phone (with IP 192.168.21.15):

nc -uv 192.168.21.15 1716

After I got the connection I copied the message into that netcat session and the phone and PC tell me that they're connected.

So my Impression is that PC and phone send UDP broadcasts (this is stated in the kdeconnect manual) and those broadcasts don't get forwarded from the phone to the pc or vice versa.

Do you have an idea on how to allow broadcast messages on USB?

[R1tschY]

Sorry, I'm not familiar with Ethernet USB. The KDE Connect Project is working on using Multicast DNS (MDNS) instead of UDP Broadcasts. Maybe is would help. However, there exists currently only a non-functioning prototype.

Also SailfishConnect is missing a option to manually select IPs to connect to. I think that would also solve your problem. Because a TCP connection is possible, right?

Currently I'm working on integrating SailfishConnect into the KDE Connect project. So there is less time for new features.

[dimpflmoser]

Haven't checked whether UDP Broadcasts or MDNS packets are forwarded. Will check that next time. Thanks!

[R1tschY]

I tested it and it connects at least for me. As a workaround in version 0.6 the IP of the computer can be added in the settings. When searching for devices a UDP packet is send to this IP address.

[R1tschY]

It is not fixed. To get this to work one has to directly connect via TCP like GSConnect does.