Made communication more robust.

router.lua

@@ -2,13 +2,30 @@
 This program should be installed on a portable computer with a wireless
 modem, to act as a routing beacon in conjunction with managed switches.
 ]]--
-local modem = peripheral.wrap("back") or error("Missing modem.")
+local SWITCH_CHANNEL = 45450
+local STATION_BROADCAST_CHANNEL = 45451
+local STATION_REQUEST_CHANNEL = 45452
+local MY_CHANNEL = 45460
 
-local STATION_CHANNEL = 1
+local g = require("simple-graphics")
+local W, H = term.getSize()
+
+local modem = peripheral.wrap("back") or error("Missing modem.")
+modem.open(MY_CHANNEL) -- Listen for messages directed to this device.
+modem.open(STATION_BROADCAST_CHANNEL) -- Listen for station broadcasts.
+
+local function serializeRoutePath(path)
+    local str = ""
+    for i, segment in pairs(path) do
+        str = str .. segment
+        if i < #path then str = str .. "," end
+    end
+    return str
+end
 
 local function broadcastRoute(route)
     while true do
-        modem.transmit(0, 42, route)
+        modem.transmit(SWITCH_CHANNEL, MY_CHANNEL, route)
         os.sleep(0.5)
     end
 end
@@ -17,22 +34,178 @@ end
 local function waitForStation(stationName)
     while true do
         local event, side, channel, replyChannel, msg, dist = os.pullEvent("modem_message")
-        if channel == STATION_CHANNEL and msg == stationName and dist <= 16 then
+        if channel == STATION_BROADCAST_CHANNEL and msg == stationName and dist <= 16 then
-            print("Arrived at station " .. stationName)
             return
         end
     end
 end
 
+local function listenForAnyStation()
+    while true do
+        local event, side, channel, replyChannel, msg, dist = os.pullEvent("modem_message")
+        if channel == STATION_BROADCAST_CHANNEL and type(msg) == "string" and dist <= 16 then
+            os.queueEvent("rail_station_nearby", msg, dist)
+        end
+    end
+end
+
+local function waitForNoStation(targetName)
+    local lastPing = os.epoch()
+    while os.epoch() - lastPing < 5000 do
+        parallel.waitForAny(
+            function ()
+                local event, name, dist = os.pullEvent("rail_station_nearby")
+                if not targetName or targetName == name then
+                    stationPresent = true
+                    lastPing = os.epoch()
+                end
+            end,
+            function () os.sleep(3) end
+        )
+    end
+end
+
+local function waitForModemMessage(expectedReplyChannel, timeout)
+    local data = nil
+    parallel.waitForAny(
+        function ()
+            while true do
+                local event, side, channel, replyChannel, msg, dist = os.pullEvent("modem_message")
+                if replyChannel == expectedReplyChannel then
+                    data = {}
+                    data.channel = channel
+                    data.replyChannel = replyChannel
+                    data.msg = msg
+                    data.dist = dist
+                    return
+                end
+            end
+        end,
+        function () os.sleep(timeout) end
+    )
+    return data
+end
+
+local function handleNearbyStation()
+    while true do
+        g.clear(term, colors.white)
+        g.drawText(term, 1, 1, "Looking for nearby station", colors.black, colors.yellow)
+        g.drawText(term, 1, 2, "Walk near a station to", colors.gray, colors.white)
+        g.drawText(term, 1, 3, "see available routes.", colors.gray, colors.white)
+        os.sleep(1)
+
+        local event, name, dist = os.pullEvent("rail_station_nearby")
+        g.clear(term, colors.white)
+        g.drawXLine(term, 1, W, 1, colors.lightBlue)
+        g.drawText(term, 1, 1, "Found a station!", colors.black, colors.lightBlue)
+        g.drawText(term, 1, 3, name, colors.blue, colors.white)
+        g.drawText(term, 1, 5, "Fetching routes...", colors.gray, colors.white)
+        os.sleep(1)
+
+        modem.transmit(STATION_REQUEST_CHANNEL, MY_CHANNEL, "GET_ROUTES")
+        local response = waitForModemMessage(STATION_REQUEST_CHANNEL, 1)
+        if not response or not response.msg or type(response.msg) ~= "table" then
+            g.clear(term, colors.white)
+            g.drawXLine(term, 1, W, 1, colors.red)
+            g.drawText(term, 1, 1, "Error", colors.white, colors.red)
+            g.drawText(term, 1, 2, "Failed to get routes.", colors.gray, colors.white)
+            if response then
+                term.setCursorPos(1, 3)
+                term.setTextColor(colors.black)
+                term.setBackgroundColor(colors.lightGray)
+                print("Response:"..textutils.serialize(response, {compact=true}))
+            end
+            os.sleep(5)
+        else
+            local routes = response.msg
+            g.clear(term, colors.white)
+            g.drawXLine(term, 1, W, 1, colors.blue)
+            g.drawText(term, 1, 1, "Routes", colors.white, colors.blue)
+            g.drawText(term, W-3, 1, "Quit", colors.white, colors.red)
+            for i, route in pairs(routes) do
+                local y = i + 1
+                local bg = colors.white
+                if i % 2 == 0 then bg = colors.lightGray end
+                g.drawXLine(term, 1, W, y, bg)
+                g.drawText(term, 1, y, i..". "..route.name, colors.black, bg)
+            end
+            -- Either wait for the user to choose a route, or go away from the
+            -- station transponder.
+            parallel.waitForAny(
+                function ()
+                    while true do
+                        local event, button, x, y = os.pullEvent("mouse_click")
+                        if button == 1 then
+                            if x >= W-3 and y == 1 then
+                                break
+                            elseif y > 1 and y - 1 <= #routes then
+                                local selectedRoute = routes[y-1]
+                                os.queueEvent("rail_route_selected", selectedRoute)
+                                return
+                            end
+                        end
+                    end
+                end,
+                function () waitForNoStation(name) end
+            )
+        end
+    end
+end
+
+local function waitForRouteSelection()
+    while true do
+        parallel.waitForAny(
+            listenForAnyStation,
+            handleNearbyStation
+        )
+        local event, route = os.pullEvent("rail_route_selected")
+        if event and type(route) == "table" then
+            return route
+        end
+    end
+end
+
 local args = {...}
 
+if #args > 1 then
     local route = args
-print("Routing via:")
+    print("Routing via command-line args:")
     for _, branch in pairs(route) do
         print("  "..branch)
     end
-
     parallel.waitForAny(
-    function() broadcastRoute(route) end
+        function() broadcastRoute(route) end,
         function() waitForStation(route[#route]) end
     )
+    return
+end
+
+g.clear(term, colors.white)
+g.drawTextCenter(term, W/2, H/2, "Rail Router", colors.black, colors.white)
+g.drawTextCenter(term, W/2, H/2 + 2, "By Andrew", colors.gray, colors.white)
+os.sleep(1)
+
+while true do
+    local route = waitForRouteSelection()
+    g.clear(term, colors.white)
+    g.drawTextCenter(term, W/2, 2, "Broadcasting route...", colors.black, colors.white)
+    g.drawText(term, 1, 4, "  Path:", colors.gray, colors.white)
+    for i, segment in pairs(route.path) do
+        local y = i + 4
+        g.drawText(term, 4, y, segment, colors.gray, colors.white)
+    end
+    g.drawText(term, W-3, 1, "Quit", colors.white, colors.red)
+
+    parallel.waitForAny(
+        function() broadcastRoute(route.path) end,
+        function() waitForStation(route.path[#route.path]) end,
+        function() -- Listen for user clicks on the "Quit" button.
+            while true do
+                local event, button, x, y = os.pullEvent("mouse_click")
+                if button == 1 and x >= W-3 and y == 1 then
+                    return
+                end
+            end
+        end
+    )
+end

station.lua

@@ -1,19 +1,66 @@
 --[[
 Stations are kiosks where users can configure their portable computer for a
 particular route to another station.
+
+You should add a "station_config.tbl" file containing:
+{
+    name = "Station name",
+    range = 8,
+    routes = {
+        {name = "First", path = {"A", "B", "C"}},
+        {name = "Second", path = {"D", "A", "C"}}
+    }
+}
 ]]--
 
 local modem = peripheral.wrap("top") or error("Missing top modem")
-local CHANNEL = 1
+local BROADCAST_CHANNEL = 45451
-local STATION_NAME = "Test Station"
+local RECEIVE_CHANNEL = 45452
 
-local function broadcastName()
+modem.open(RECEIVE_CHANNEL)
+
+local function readConfig()
+    local f = io.open("station_config.tbl", "r")
+    if not f then error("Missing station_config.tbl") end
+    local cfg = textutils.unserialize(f:read("*a"))
+    f:close()
+    return cfg
+end
+
+local function broadcastName(config)
     while true do
-        modem.transmit(CHANNEL, CHANNEL, STATION_NAME)
+        modem.transmit(BROADCAST_CHANNEL, BROADCAST_CHANNEL, config.name)
         os.sleep(1)
     end
 end
 
+local function handleRequests(config)
+    while true do
+        local event, side, channel, replyChannel, msg, dist = os.pullEvent("modem_message")
+        if channel == RECEIVE_CHANNEL and dist <= config.range then
+            if msg == "GET_ROUTES" then
+                modem.transmit(replyChannel, RECEIVE_CHANNEL, config.routes)
+                print(textutils.formatTime(os.time()).." Sent routes to "..replyChannel)
+            end
+        end
+    end
+end
+
+local config = readConfig()
+term.clear()
+term.setCursorPos(1, 1)
+print("Running station transponder for \""..config.name.."\".")
+print("  Range: "..config.range.." blocks")
+print("  Routes:")
+for i, route in pairs(config.routes) do
+    local pathStr = ""
+    for j, segment in pairs(route.path) do
+        pathStr = pathStr .. segment
+        if j < #route.path then pathStr = pathStr .. "," end
+    end
+    print("   "..i..". "..route.name..": "..pathStr)
+end
 parallel.waitForAll(
-    broadcastName
+    function() broadcastName(config) end,
+    function() handleRequests(config) end
 )

switcher.lua

@@ -6,7 +6,7 @@ will decode it and make any adjustments it needs to.
 ]]--
 
 local CONFIG_FILE = "switch_config.tbl"
-local CHANNEL = 0
+local CHANNEL = 45450
 local config = nil
  
 local modem = peripheral.wrap("top") or error("Missing top modem")
@@ -15,7 +15,7 @@ modem.open(CHANNEL)
  
 term.clear()
 term.setCursorPos(1, 1)
-print("Receiving routing commands on channel 0")
+print("Receiving routing commands on channel " .. CHANNEL)
 
 -- Series of guided inputs for building a configuration file from user input.
 local function configSetupWizard()
@@ -156,10 +156,6 @@ end
 -- Handles incoming rail messages that consist of a list of branch names
 -- that the user would like to traverse.
 local function handleModemMsg(replyChannel, msg)
-    if type(msg) == "string" and msg == "PING" then
-        modem.transmit(replyChannel, CHANNEL, "PONG")
-        return
-    end
     -- Ignore invalid messages.
     if not msg or #msg < 2 then return end
     -- Find the switch configuration(s) that pertain to this route.