Use lighttpd as a proxy-pass server

$HTTP["host"] =~ "made.up.hostname" { # hostname you want to create
    $SERVER["socket"] == ":1234" { # port you want to create

        server.errorlog      = "/var/logs/madeup/lighttpd-error.log"
        accesslog.filename   = "/var/logs/madeup/lighttpd-access.log"

        proxy.server = ( "" =>
                           ( ( 
                               "host" => "123.456.789.012", # where you want to proxy to
                               "port" => 5678, # port you want to proxy to
                             ) ) 
                         )   
    }   
}

# Now go to http://made.up.hostname:1234 and you will get directed through to http://123.456.789.012:5678