UDP to TCP converter

[rchdee17]

Is this possible with the Raspberry Pi protocol stacks? Reading in data from a UDP protocol thru either ethernet port or usb, then sending it out via the TCP protocol? What I am trying to do is not practical from my viewpoint, but the Weather Center has approached our senior development group for a way to be the middle man between a weather radar and a radar office. They are trying to combine the benefits of realtime checkless UDP protocol with the reliable, slower TCP protocol. The idea they have is to receive radar data coming in with a UDP protocol, and transmit the data out on a TCP protocol to prevent data loss i.e. drops in the unrealiable T1 line. The also wanted a buffer (could be done through the RPi's RAM?) to keep data that would otherwise be lost from some sort of brief outage (no longer than 6 minutes) and then retransmit the data after the connection comes back up.

Thoughts?

P.S. This was previously accomplished by wiring a ethernet port to an mBed microproc using UDP listener socket, then transmitting that data via SPI to a second mBed, then transmitting out thru a TCP socket.

[ghans]

This sounds like a programming exercise , but definitely doable.

Do you have any experience with programming ?

ghans

[rchdee17]

This sounds like a programming exercise , but definitely doable.

Do you have any experience with programming ?

ghans

Yes I have programmed with Java, C, and C++, but never Python and am not that familiar with Linux. I am thinking UDP -> ethernet to USB adapter -> RPi usb -> store data on RAM -> transmit over ethernet out via TCP

[ghans]

Is there a necessity for a USB Ethernet adaptor ? The Pi's ethernet is internally already connected to Ethernet.

ghans

[ghans]

I meant USB , of course. That is the cause for bandwith limitations.
ghans

[gt40mkii]

This is relatively straight forward and can be done a few ways:

1. Write a socket program that reads the UDP data (you'll need to know what port to listen on and whether the data is being sent to a specific IP address, sent to a multicast address, or broadcast.) Once you have the packet, you can then send it over a TCP socket to a custom server running on the remote machine. Of course you'll have to implement your own buffering to handle disconnects. Once the far side gets disconnected, your TCP socket will close.
2. Write a simple C program to read the UDP traffic and drop it into a specific directory -- one file per packet. then have a script monitor that directory. Once a file shows up, transmit it to the remote machine via scp (secure, encrypted file transfer implemented on top io TCP,) Oncve the file weas successfully transmitted, delete the local file. This way if the remote machine goes down, packets will accumulate on the local machine until the remote machine comes up, then all the files that backed up will be transmitted. You'll need some kind of monitoring daemon running to clear out very old files in order to keep from filling up your file sytem, though.

If it were me, I'd opt for #2.

[sej7278]

have you looked at using sctp instead?

[gridrun]

Just use a buffer (memory area). Read UDP datagrams coming in, store them to the buffer as they arrive. Periodically send the contents of the buffer via TCP. There should be no need for an additional Ethernet interface (unless the networks need to be physically separated from each other, perhaps due to security reasons).

[gridrun]

You could even use http://de.wikipedia.org/wiki/Netcat to do this.

[ghans]

Netcat/socat was on my mind too.

ghans

[rchdee17]

Thanks guys. Will test this stuff out as soon as we get the RPi and let you know how it goes.