R socketConnection/make.socket(): any way to keep listen()ing?

Question

[Disclaimer: my knowledge of sockets is very rusty, and I'm just getting into R, so if I missed something completely obvious, please point it out!]

If I understand the (sparsely-documented) R functions for creating and managing sockets, namely socketConnection and make.socket, it appears that when creating a server socket (server=TRUE), the moral equivalent of the following is carried out:

s = socket(yada yada);
listen(s, ...);
s2 = accept(s, ...);
close(s, ...);

and now I can work with s2 but can't loop to deal with a backlog of incoming connections to s. Is this more-or-less right? Is there any way to keep listening and continue to deal with additional incoming connections after handling the first?

Answer 1

I'd like to know the answer to this one too! ...but in the meantime I can at least suggest a work-around with some limitations:

If you can know HOW MANY clients will connect, then the following should work.

On the server:

n=2         # Number of clients
port=22131

slist=vector('list',n)
# Connect to all clients
for(i in 1:n) slist[i] <- socketConnection('localhost', port=port, server=TRUE)

# Wait for a client to send data, returns the client index 
repeat {
  avail <- which( socketSelect(slist) )[[1]]
  # ...then read and process data, rinse, repeat...
}

On each client:

port=22131
# Connect to server
s <- socketConnection('localhost', port=port)
# ...then send data...
writeLines(c('foo', 'bar'), s)