used new example with pipe based telnet server

telnet.lua

@@ -1,54 +1,51 @@
 -- Telnet client 
-telnetClient=nil
-local lines = {}
+--[[  A telnet server   T. Ellison,  June 2019
 
--- Helper function
-function s_output(str)
-      uart.write(0,  "T:" .. tostring(str))
-      if (telnetClient ~= nil) then
-	if (#lines > 0) then
-	    table.insert(lines, str)
-	else
-	    table.insert(lines, str)
-	    telnetClient:send("\r") -- Send something, so the queue is read after sending
-	end
-      end
-end
+This version of the telnet server demonstrates the use of the new stdin and stout
+pipes, which is a C implementation of the Lua fifosock concept moved into the
+Lua core.  These two pipes are referenced in the Lua registry.
 
--- Telnet Server
-function startTelnetServer()
-    s=net.createServer(net.TCP, 180)
-    s:listen(23,function(c)
-	    telnetClient=c
-	    node.output(s_output, 0)
-	    c:on("receive",function(c,l)
-	      node.input(l)
-	    end)
-	    c:on("disconnection",function(c)
-	      node.output(nil)
-	      telnetClient=nil
-	    end)
-	    c:on("sent", function()        
-		if (#lines > 0) then
-		  local line1=nil
-		  for k,v in pairs(lines) do if (k==1) then 
-			  line1=v 
-		  	end
-			uart.write(0, "Lines:" .. tostring(v) .. "\r\n")
+]]
+--luacheck: no unused args
 
+local telnetS = nil
+
+local function telnet_session(socket)
+  local node = node
+  local stdout
+
+  local function output_CB(opipe)   -- upval: socket
+    stdout = opipe
+    local rec = opipe:read(1400)
+    if rec and (#rec > 0) then socket:send(rec) end
+    return false -- don't repost as the on:sent will do this
   end
-		  if ( line1 ~= nil ) then
-		   table.remove(lines, 1)
-		   uart.write(0, "Telent[" .. tostring(#lines) .. "]" .. tostring(line1) .. "\r\n" )
-		   telnetClient:send(line1)
+
+  local function onsent_CB(skt)     -- upval: stdout
+    local rec = stdout:read(1400)
+    if rec and #rec > 0 then skt:send(rec) end
   end
+
+  local function disconnect_CB(skt) -- upval: socket, stdout
+    node.output()
+    socket, stdout = nil, nil -- set upvals to nl to allow GC
   end
-	    end)
-	    print("Welcome to the Wordclock.")
+
+  node.output(output_CB, 0)
+  socket:on("receive", function(_,rec) node.input(rec) end)
+  socket:on("sent", onsent_CB)
+  socket:on("disconnection", disconnect_CB)
+    print( ("Welcome to the Wordclock. (%d mem free, %s)"):format(node.heap(), wifi.sta.getip()))
     print("- mydofile(\"commands\")")
     print("- storeConfig()")
     print("Visite https://github.com/nodemcu/nodemcu-firmware/wiki/nodemcu_api_en for further commands")
     uart.write(0, "New client connected\r\n")
-    end)
+end
+
+
+-- Telnet Server
+function startTelnetServer()
+    telnetS=net.createServer(net.TCP, 180)
+    telnetS:listen(23, telnet_session)
     print("Telnetserver started")
 end