NMEA from Cobham AIS using multicast address

[iraznatovic]

Good day to all,

This is my first post on the forum. I just installed a Cobham Sailor 6282 AIS and all works fine. I wanted to connect my laptop (win7) to it and display AIS data in OpenCPN but I seem to be missing something.

I am not using a serial connection, and would like to avoid it for now since Sailor has ethernet connection. I want to explore that option. The manual mentions the follwing:

Light weight Ethernet - LWE
Sentences may be configured to be received and transmitted over serial PI and sensor
interfaces, but also over Light Weight Ethernet (IEC 61162-450). The following table shows the available transmission group multicast addresses and ports that can be set up in the Service Interface.



There are more addresses listed but I didn't list them. So the question is - how do I set up the connection in OpenCPN to view the data?

[CarCode]

I doubt OpenCPN is intended for a Class A transponder. Usually pleasure boats have Class B only.

Gerhard

[bcn]

Where is the problem with Class A?
The NMEA sentences are identical.

The interesting point here is the data (format) transmitted via Ethernet by this unit. Contents and format of the transmission groups.

iraznatovic, do you have documentation which details the contents?

IEC 61162-450
Multiple talkers Multiple listeners

This subgroup of TC80/WG6 has specified the use of Ethernet for shipboard navigational networks. The specification describes the transport of NMEA sentences as defined in 61162-1 over IPv4. Due to the low amount of protocol complexity it has been nicknamed Lightweight Ethernet or LWE in short.

The historical background and justification for LWE was presented at the ISIS2011 symposium.[2] An overview article of LWE was given in the December issue of "Digital Ship" [3]

The standard was published in the first edition 06/2011 . The second edition is in progress(state 05/2016).
......
-1 is Part 1: Single talker and multiple listeners (Also known as NMEA 0183)[

Some background here:
http://www.mits-forum.org/resources/...er-isis-v9.pdf

[Hakan]

iraznat.....
Based on your info and Hubert's info/link I should have test the following:
1) Get a Internet switch and set it to use IP segment: 239.192.0.0. You may let it act as a DHCP server.
2) Connect your AIS and OCPN PC to the switch. If DHCP on the switch set your PC to acquire DHCP IP address.
3) Add two network UDP connections in OCPN. One for IP address 239.192.0.2 port 60002 (TGTD) and the other 239.192.0.4 port 60004 (NAVD)

For AIS data TGTD would be priority one but it may be the GPS data from the AIS are broadcast as NAVD.

Good luck
Håkan

[CarCode]

Originally Posted by Hakan

1) Get a Internet switch and set it to use IP segment: 239.192.0.0. You may let it act as a DHCP server.

Do you have a link for an IP Switch which can act as a DHCP server?
I really search for such a device and hopefully not expensiv.

Gerhard

[oxygen]

In my expierence with t&t/cobham whoever it made , all sailors products got dedicated lan port only for themselves. you can connect for example inmarsat terminal, radar or vdr or whatever you want but proppably u just cant use it like rs port. Just buy junction box (6283) dedicated to this product and problem will be solved.

Best regards
Maciej

[Hakan]

Gerhard.
Yes the switch in a router will do. Ok - to short wording but without the router no DHCP that's rather obvious? And without DHCP a fix IP address on the PC.
Kind of you correcting given facts.
Håkan

[did-g]

Originally Posted by Hakan

iraznat.....
Based on your info and Hubert's info/link I should have test the following:
1) Get a Internet switch and set it to use IP segment: 239.192.0.0. You may let it act as a DHCP server.
2) Connect your AIS and OCPN PC to the switch. If DHCP on the switch set your PC to acquire DHCP IP address.
3) Add two network UDP connections in OCPN. One for IP address 239.192.0.2 port 60002 (TGTD) and the other 239.192.0.4 port 60004 (NAVD)

For AIS data TGTD would be priority one but it may be the GPS data from the AIS are broadcast as NAVD.

Good luck
Håkan

Any reason for the DHCP server? 239 is a multicast IP and since 2014 OCPN set the right socket option so it should work with any switch and any client IP, it may or may not work over wifi though.

[muttnik]

IEC 61162? That's not something you normally encounter in the cheap seats!

I've not seen the spec but if as I think it's simlply nmea-0183 over multicast ethernet just set up a normal network connection with the address and ports specified. As did-g says, no need for special interface address. Should be no problem with wifi: even with multicast snooping on your switch OCPN should be joining the group correctly.

Firewalling might be an issue. Don't know much about how windows firewall works if an application joins a multicast group but IIRC OpenSuSE used to be pretty braindead in that respect.

You might also encounter problems if trying to receive multicast over an interface which isn't your default route for multicast but hopefully that isn't a common case

I'd be very interested to know if this works: please do update us.

[iraznatovic]

This is the page I think is relevant, but the manual is available here (https://www.google.com/url?q=http://www.pacificrim.com.au/media/custom/upload/File-1400203403.pdf&sa=U&ved=0ahUKEwin-f70srbSAhWDWSwKHUyfDtwQFggLMAA&usg=AFQjCNHBzlcDg9m zyS8LVMcwuq5_6yHtwQ)

[iraznatovic]

I used wireshark to check if I am getting any packets from AIS on the network & yes, I could see from my laptop the address 239.192.0.2 sending data over port 60002.
This was without any switch between the transponder, Sailor Control panel (android based device used to display ais data) & my laptop since transponder has 2 ethernet ports, and I guess, acts as a switch.

[barnakiel]

It seems like it is the "2" indeed - target data sounds reasonable.

Plug into the OpenCPN set up and see what ensues.

b.

[iraznatovic]

Originally Posted by barnakiel

It seems like it is the "2" indeed - target data sounds reasonable.

Plug into the OpenCPN set up and see what ensues.

b.

This is what i tried in OpenCPN without results:

• Check "Show NMEA Debug Window"
• Add connection
• Switch to "Network"
• Protocol: UDP
• Address: 239.192.0.2
• DataPort: 60002

All else blank. This did not work. I mad couple of variations by adding all sentences in "Accept only sentences" field, and trying TCP using IP of the transponder (192.168.137.15) and no port number, but, alas with same result.

[did-g]

Originally Posted by iraznatovic

This is what i tried in OpenCPN without results:

• Check "Show NMEA Debug Window"
• Add connection
• Switch to "Network"
• Protocol: UDP
• Address: 239.192.0.2
• DataPort: 60002

All else blank. This did not work. I mad couple of variations by adding all sentences in "Accept only sentences" field, and trying TCP using IP of the transponder (192.168.137.15) and no port number, but, alas with same result.

Hi
Can you disable your firewall if any?
if it still doesn't work then capture the traffic with wireshark, start opencpn with the network setting and put it somewhere with your opencpn.log.

[Hakan]

Originally Posted by iraznatovic

I used wireshark to check if I am getting any packets from AIS on the network & yes, I could see from my laptop the address 239.192.0.2 sending data over port 60002.
This was without any switch between the transponder, Sailor Control panel (android based device used to display ais data) & my laptop since transponder has 2 ethernet ports, and I guess, acts as a switch.

Wireshark - good.
Can you also see if there is something looking as NMEA 0183 messages?
This is the basic test. No NMEA 0183 no interpretation in OCPN!
If so I think you've to go back to oxygen's post above. It could be some internal messages instead of NMEA 0183.

If you find good NMEA 0183 messages then it's all about network handling.
Håkan