server_open ?option? host service
              Open a TCP/IP connection to a server of host on the
              port specified by  service.   The  server  is  then
              accessed  using the standard Tcl file I/O commands.
              Host may be a host name or an IP address.  Port may
              be  a port number of a service name.  Option is one
              of -buf or -nobuf.  If  no  options  is  specified,
              -buf is the default.

              If  -buf  is  specified, then the file is buffered.
              In this case, a pair of Tcl file ids  are  returned
              in  a  list.  The first id is open for read access,
              the second for write.  When writing  to  the  file,
              the flush command must be used to force data in the
              buffer to be sent to the server.  The close command
              must  be  called against both file ids when through
              with the socket.  Buffered access  will  result  in
              significantly  better performance when reading data
              and will also improve a series of writes being done
              with  out  intermixed reads.  The fcntl command may
              be used to make one of these files unbuffered.

              If -nobuf is specified, then the file is unbuffered
              and  a  single  file  id, open for both reading and
              writing, is returned.

              If a host  name  is  supplied  and  more  that  one
              address  is  valid for the host, the addresses will
              be tried until one can be connected  to.   Use  the
              server_info  command  to  obtain  the list of valid
              address.

              This command is provided by Extended Tcl.