[SOLVED] Connecting to Remote J-Link via IP not resolving

travis_spidertracks · Apr 8th 2021, 1:19am

Hi there,

I have been using a J-Link running v6.50b. My development environment is inside a linux Docker container, and the Host OS is Windows 10. I run the J-Link remote server on the host with the J-Link connected via USB and connect from inside the container using JLinkeExe -ip host.docker.internal which has been working fine. Recently I upgraded the segger tools to version 6.98c and it has stopped working.

My docker container still resolves the address using ping

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ping host.docker.internal
PING host.docker.internal (192.168.65.2) 56(84) bytes of data.
64 bytes from 192.168.65.2 (192.168.65.2): icmp_seq=1 ttl=37 time=1.15 ms
64 bytes from 192.168.65.2 (192.168.65.2): icmp_seq=2 ttl=37 time=1.48 ms
64 bytes from 192.168.65.2 (192.168.65.2): icmp_seq=3 ttl=37 time=1.19 ms

And can connect using the hard coded address

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JLinkExe -NoGui 1 -ip 192.168.65.2
SEGGER J-Link Commander V6.98c (Compiled Mar 16 2021 12:23:05)
DLL version V6.98c, compiled Mar 16 2021 12:22:49
Connecting to J-Link via IP...JLinkGUIServerExe: cannot connect to X server
O.K.

But does not connect using the host.docker.internal name anymore

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JLinkExe -NoGui 1 -ip host.docker.internal:19020
SEGGER J-Link Commander V6.98c (Compiled Mar 16 2021 12:23:05)
DLL version V6.98c, compiled Mar 16 2021 12:22:49
Connecting to J-Link via IP...FAILED: Cannot connect to J-Link name host.docker.internal via TCP/IP. No emulators found.
Cannot connect to J-Link.

What I notice is that the error is

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Cannot connect to J-Link name host.docker.internal via TCP/IP

But if I type a wrong IP it gives

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JLinkExe -NoGui 1 -ip 192.168.65.3
SEGGER J-Link Commander V6.98c (Compiled Mar 16 2021 12:23:05)
DLL version V6.98c, compiled Mar 16 2021 12:22:49
Connecting to J-Link via IP...FAILED: Can not connect to J-Link via TCP/IP (192.168.65.3, port 19020)
Cannot connect to J-Link.
J-Link>

Almost like it is treating the host.docker.internal as the name of a J-Link even though it is passed in with the -ip.

Can anyone shed some light on this and how I can fix?

Thanks
Travis

SEGGER - Alex · Apr 10th 2021, 12:59am

Hi,

You are confusing J-Link name with hostname here.
The -ip <Name> command was never meant to resolve hostnames but was meant to resolve J-Link nick names to an actual IP.
J-Links can be discovered via a special UDP broadcast packet in LAN (This is what J-Link Configurator does to find and list them).
The response also contains the nickname of the J-Link.

The hostname of your machine / VM / docker container etc. is something completely different.
IP connections made by J-Link utilities are not aware of any hostname.
If it was working in the past, it was a bug. (Probably a bug that the name was taken as a hostname instead of a J-Link nickname, so nicknames did not work but were documented to be working).

Connecting to a J-Link Remote Server instance is not different for any J-Link utility. It is handled the same as a IP J-Link (like J-Link PRO).
The difference on the low-level is that Remote Server is currently not discoverable via the special UDP broadcast packet, so -ip <Nickname> won't work for Remote Server connections, only -ip <IP> does.

Short:
This is no regression, as it was never meant to work.
You may run a tool to do hostname resolving before starting J-Link Commander and pass the actual IP to it.

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