[[Explain why [ftp] is probably better choice, or [tls], or an [exec] of [ssh], or...]













----
Here's one demonstration:
    # This is server.tcl.

    # This is a model implementation of file-copying through Tcl's [socket]
    #    facilities.  What follows is the server process, which receives
    #    files through network connections, and deposits them in
    #    $destination_directory.

    # A production version of this model would probably expose parameters,
    #    handle exceptions more gracefully, consider security, and so on.
    #    The purpose of this code is primarily pedagogic.


        # You might want this to come from a command-line argument,
        #    or environment variable, or even let the clients pass
        #    it in.
    set destination_directory /tmp


        # A command-line argument is probably a good way to specify this.
    set service_port  3456


    proc receive_file {channel_name client_address client_port} {
        fconfigure $channel_name -translation binary
        gets $channel_name line
        foreach {name size} $line {}

        set fully_qualified_filename [file join $::destination_directory $name]
        set fp [open $fully_qualified_filename w]
        fconfigure $fp -translation binary

        fcopy $channel_name $fp -size $size

        close $channel_name
        close $fp
    }


    socket -server receive_file $service_port

    vwait forever


And here's the second half:
    # This is client.tcl.

    # Invoke as "client.tcl <filename>" (for a local file).


    set service_port 3456
    set service_host starbase.neosoft.com ;# Old web site - need to change!

    proc send_one_file name {
        set size [file size $name]
        set fp [open $name]
        fconfigure $fp -translation binary

        set channel [socket $::service_host $::service_port]
        fconfigure $channel -translation binary
        puts $channel [list $name $size]

        fcopy $fp $channel -size $size

        close $fp
        close $channel
    }

    send_one_file $argv






[[other uses of [socket].]]




----
[[Make link to cool [Expect] example.]]





[[Steve Ball's book has chapter on client-server programming.]]



[Dennis LaBelle] has an example
[http://home.nycap.rr.com/dlabelle/TCL/samples/server/].