Port example: Send block to Server, Responds with reversed block.

ping.reb

#!/usr/local/bin/ren-c

Rebol [
    Title: "Ping Scheme"
    Date:  5-Jan-2017
    Author: "Christopher Ross-Gill"
    Home: https://github.com/revault/rebol-wiki/wiki/Port-Examples#tcp-ping-pong-messages
]

sys/make-scheme [
    Title: "Ping Client"
    Name: 'ping
    Actor: [
        Write: func [port data /local subport][
            wait open subport: make port! [
                scheme: 'tcp
                host: port/spec/host
                port-id: port/spec/port-id
                awake: func [event][
                    switch event/type [
                        lookup [
                            open event/port
                            false
                        ]
                        connect [
                            write event/port to binary! mold data
                            false
                        ]
                        wrote [
                            read event/port
                            false
                        ]
                        done [event/port/data: read event/port true]
                    ]
                ]
            ]
            wait 0.01 ; surely this shouldn't be needed
            any [
                attempt [load subport/data]
                [fail]
            ]
        ]
    ]
]

probe write ping://127.0.0.1:8000 [foo bar]

pong.reb

#!/usr/local/bin/ren-c

Rebol [
    Title: "Pong Scheme"
    Date:  5-Jan-2017
    Author: "Christopher Ross-Gill"
    Home: https://github.com/revault/rebol-wiki/wiki/Port-Examples#tcp-ping-pong-messages
]

sys/make-scheme [
    Title: "Pong Server"
    Name: 'pong
    Actor: [
        open: func [port][
            print ["Opening Server:" port/locals: rejoin [tcp://: port/spec/port-id]]
            port/locals: open port/locals
            port/locals/awake: func [event /local client][
                if event/type = 'accept [
                    client: first event/port
                    client/awake: func [event /local message] [
                        ;probe event/type
                        switch event/type [
                            read [
                                message: probe attempt [load event/port/data]
                                clear event/port/data
                                write event/port to binary! mold probe either message [
                                    compose/only [ok (reverse compose [(message)])]
                                ][
                                    [fail]
                                ]
                                return false
                            ]
                            wrote [
                                print "Server sent pong to client"
                                close event/port
                                return true
                            ]
                            close [
                                close event/port
                                return true
                            ]
                        ]
                        false
                    ]
                    read client
                ]
                false
            ]
            port
        ]

        close: func [port][
            close port/locals
        ]
    ]
]

wait open pong://:8000