How to pull NMEA info from one laptop onto the other?

[LifePart2]

We have OpenCPN running on our little windows 8 Acer. It receives NMEA input from a bluetooth connection, via PolarCom (see other threads about OpenCPN not seeing bluetooth inputs for the reason we are doing it that way).

When I had a friend over to set this all up, we also had it set up so that the second laptop was able, via a wifi network connecting the two laptops, to receive that same NMEA data from the first laptop. I believe it was done by setting a TCP connection in OpenCPN on the second laptop, and setting up PolarCom to output the NMEA data to an IP address on the first laptop.

The trouble is, I can't remember how it was all set up. What IP addresses do I put in the two connection settings? I see I have a connection for 127.0.0.1 in OpenCPN on laptop 2, but that doesn't seem to do anything. I think that was for running PolarCom on the same machine, not the other machine. Can anyone tell me how I achieve this again, so that laptop 2 can see the NMEA data that is comming into PolarCom on laptop 1 (both windows 8)?

Thanks

[barnakiel]

You link the two devices via wifi (I believe on Windows XP it is an ad-hoc connection, but I know that Windows 8 have hot-spot capacity too). Then look up what IP they are using. One machine will be the host (server) the other will be the client. Normally, it is the server that assigns the IP to the client unless you use a static IP on the client side (I do not, I just let the server dynamically assign the IP to the client).

On server software side: have the software (OpenCpn, PolarCom, NavMon, whatever) output the required data to this IP. Set the data port (I do not know what these are but we use any port number and they all seem to work all the same).

On client software side: have the software read IP established by the server, use the same data port. And that's that. I think.

The above holds true for Windows / Android and I bet any other platform too.

I believe if using UDP rather than TCP, you skip the port number part.

b.

[damianham]

127.0.0.1 is the localhost IP address i.e. that is for connecting to services on the local laptop only. I couldn't find a user manual on the PolarNavy site for PolarCOM but the list of features include

Forwarding and receiving data over TCP/UDP network connections

So it should be straight forward to work out how to setup PolarCOM and OpenCPN to send NMEA data from PolarCOM on laptop 1 to OpenCPN on laptop 2.

Open a command prompt on laptop 2 and type ipconfig , that will list the network devices and the IPV4 addresses for each device. On laptop 1 setup PolarCom to transmit the NMEA data to the IP address for laptop 2.

If you need to know what ports OpenCPN on laptop 2 is listening and there is no configuration screen in OpenCPN to set it up then in the command prompt window type netstat /a /n and that will list the open TCP ports and their state. Look for a line that has LISTENING in the right hand column.

In the 2nd column is the IP address and port the software is listening on in the format <IP address>:<port number> . In most cases the IP address will be 0.0.0.0 which means listen on all IP addresses on all devices - so use the IP address from ipconfig.

UDP does use ports - it differs from TCP in that it is not stream based (i.e. there is no connection established)

[barnakiel]

Originally Posted by damianham

(...) UDP does use ports - it differs from TCP in that it is not stream based (i.e. there is no connection established)

I stand corrected. It does.

b.

[LifePart2]

Thanks folks,

Very helpful