G'Day,

I came across a library a little while ago which provided some useful features for a project I am working on --- it would save a few days work, and a lot of bug testing, so you can see why I want to use it --- but it relies on serial communication, whereas I want to so everything via ethernet (because the serial port is already tied up). I would imagine adding ethernet support to these functions would be relatively simple, but I am a little stuck here.

I searched this forum the other day, and came up with libpcap, which sounded nice, however, as I get deeper into it, I get the feeling it is not quite what I need. While libpcap has some nice features for reading packets, what I want is simple receive and transmit of data between two systems: libpcap seems to have more than I need for receive, and does not seem to support transmit.

Obviously there would be something already out there (likely a heck of a lot simpler than I am thinking too), but I am a little stuck now as to what I need to do. If I could be directed to any HOWTOs or other guides which explain how to use ethernet in a C program, I would be really grateful.

Thanks!

Hello.

as you have found, libpcap is pretty much just for sniffing packets on the wire. I am not sure how low-level you want to get, but I would start with "man socket" which will describe how to open a file-like descriptor to read or write data over the wire.

Here is a short tutorial to get you going:
http://www.linuxgazette.com/issue47/bueno.html

google "socket programming C linux" for more...

That seems to be what I was after! Thanks for your time

I have made use of this document to extend the library I had found, and everything works fine, except for one point I had not thought about before it happened. If enough clients connect to the server, further connections will be refused --- which makes sense --- but what about if all the currently connected clients have used close(fd)? How do I know when the server should close() the socket returned by accept(), and therefore be prepared to accept() future connections? Is there a simple way to know that the client has disconnected, or should there be some protocol whereby the client says "bye" before they call close()? I have thought about time outs, which would not be a bad idea to add, but there should surely be a cleaner option for when the client leaves like this.