Rserve is a server which allows other programs to use the facilities of R via TCP/IP.
Installing
Since Rserve gets installed to system folders, you need to do the install as the root user.
# Become root.
$ sudo su
# Run R as root.
$ R
> install.packages("Rserve")
Running
To launch as a daemon.
$ R CMD Rserve
To launch in debug mode.
$ R CMD Rserve.dbg