min-httpd.reb

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

Rebol [
    Title: "Minimal HTTPD 404 Server"
    Date: 17-Mar-2017
]

sys/make-scheme [
    title: "Minimal 404 Server"
    name: 'httpd

    locals: make object! [
        server-port: listen-port: _

        awake-client: func [event /local client] [
            client: event/port
            switch event/type [
                read [
                    either find client/data to-binary "^M^/^M^/" [
                        probe to string! client/data
                        write client #{
                            485454502F312E3020343034204E6F7420466F756E640D0A436F6E74656E742D
                            547970653A20746578742F706C61696E0D0A436F6E74656E742D4C656E677468
                            3A20390D0A0D0A4E6F7420466F756E64
                        }
                    ][
                        read client
                    ]
                ]
                wrote [close client]
                close [close client]
            ]
        ]
    
        awake-server: func [event /local client] [
            if event/type = 'accept [
                client: first event/port
                client/awake: :awake-client
                read client
            ]
        ]
    ]

    actor: [
        open: func [port [port!]][
            port/locals: make port/scheme/locals [
                server-port: :port
                listen-port: open rejoin [tcp://: port/spec/port-id]
                listen-port/awake: function [event][server-port/awake event]
            ]
            port/awake: get in port/locals 'awake-server
            port
        ]
    ]

    awake: _
]

httpd: open httpd://:8080
wait [httpd]