Version:0.9 StartHTML:0000000105 EndHTML:0000050648 StartFragment:0000001053 EndFragment:0000050632 mXScriptasHTML 
program HelloWorldWebServerX4_Arduino_Sensor;
 
//{$APPTYPE CONSOLE minimal -extend autotimer IP Hoster to Arduino event}
// get a temp value from arduino to serve with socks on a browser
//#sign: max: MAXBOX8: 18/01/2017 18:48:51 
//uses SysUtils, IdContext, IdCustomHTTPServer, IdHTTPServer;

Const
  COMPORT = 'COM3';
  IPPORT = 8080;
  LOGFILE = 'arduino_temp36log7.txt';
  JSCRIPT = 'C:\maXbox\softwareschule\IBZ_2016\IBZ_Prozesstechnik_2016\Uebungen\date_time.js';

  var hlog1: THotlog;
      artimer: TTimer;
      jsload, tmpval,tmp2,aremoteip, HStarttime: string;
      
function connectAndGetValue: string; forward;    

procedure HTTPServerCommandGet(thread: TIdPeerThread;
            ReqInfo: TIdHTTPRequestInfo; RespInfo: TIdHTTPResponseInfo);
begin
   RespInfo.ResponseNo:= 200;
   //RespInfo.ContentText:= 'IBZ TimeTempServe: '//charset=UTF-8'
   //                   +DateTimeToInternetStr(Now,true)+': '+tmpval;
   reqinfo.document := exepath+'/';
   aremoteip:= ReqInfo.remoteIP;
   RespInfo.ContentType:= 'text/HTML';
   RespInfo.ContentText := '<!DOCTYPE html><html><head>'+
   '<META HTTP-EQUIV="Refresh" CONTENT=5>'+
   '<title>My Arduino mXResponse</title>'+
   //'<script type="text/javascript" src="date_time.js"></script>'+
  '<script type="text/javascript">'+jsload+'</script>'+
    CRLF+'</head>'+CRLF+'<body>'+CRLF+
  '<h1>Welcome OpenC° & maXbox4 temptime </h1>'+
  '<h1>************************************</h1>'+
  'Command: ' +ReqInfo.Command+' of Temperature C°: <b>'+tmpval+'</b>'+
  '<p><br>Host: ' + ReqInfo.Host + ' C°: '+tmp2+
  '<br>RemoteIP: '+ ReqInfo.remoteIP +
  '<br>Version: ' + ReqInfo.Version +
  '<br>Docpath: ' + ReqInfo.Document +
  '<br>Client: <span id="date_time"></span>'+
  '<script type="text/javascript">window.onload=date_time(''date_time'');</script>'+
  '<br>Host Starttime: '+ HStarttime+
  '<br>URI: ' + ReqInfo.URI +
  '<br>ServerContent SW: '+RespInfo.ServerSoftware+
  '<br>UserAgent: ' + ReqInfo.UserAgent+'</p>'+
  '<IMG SRC="http://www.softwareschule.ch/images/atom_ani.gif"'+
  ' ALIGN="BOTTOM" BORDER="0" COLOR="#fffed3">'+
  '</body></html>';  //*)
   tmp2:= tmpval; 
   hlog1.AddStr(DateTimeToStr(Now)+': '+tmpval+'>'+ReqInfo.remoteIP);
end;

procedure eventActTimer(sender: TObject);
begin
  tmpval:= connectAndGetValue;
  writeln(datetimetostr(now)+' C°: '+tmpval+'° >'+aremoteIP)
end;  
  
procedure StartLogger;
begin
   if not FileExists(ExePath+LOGFILE) then begin
     CloseFileHandle(FileCreate(ExePath+LOGFILE));
     sleep(500);
   end; 
   hlog1:= THotlog.create;
   hlog1.hlWriter.hlFileDef.filename:= LOGFILE;
   hlog1.hlWriter.hlFileDef.path:= exepath;
   hlog1.hlWriter.hlFileDef.append:= true; 
   writeln('Logfile: '+hlog1.hlWriter.hlFileDef.filename)
   //SetHotLogHeader(hlog1); 
   hlog1.StartLogging; 
   sleep(200)
   hlog1.Add('>>>> Start {App_name} v {App_ver}{40@}{now}');
   hlog1.Add('{@12}From : '+'maxform1.appname');
 end; 
 
function connectAndGetValue: string;
 begin
   with TBlockSerial.Create do begin
     Config(9600,8,'N',1,true,false);
     Connect(COMPORT);
     result:= RecvString(1800)   //com timeout
     CloseSocket;
     Free;
   end;  
end; 
 
begin   //@main
  jsload:= filetostring(JSCRIPT)
  tmp2:= '0';
  HStarttime:= DateTimeToInternetStr(Now,true)
  //TWebServerCreate;
  with TIdHTTPServer.Create(Nil) do begin
    sr:= GetIPfromHost(getHostName)  //'172.16.10.80';
    try
      Bindings.Add.IP:= sr; 
      Bindings.Add.Port:= IPPORT;
      OnCommandGet:= @HTTPServerCommandGet;
      Active:= True;
    except
      writeln(ExceptionToString(ExceptionType, ExceptionParam)); 
      Active:= False; Free;
    end;   
    try
      StartLogger;
      If IsCOMPort then begin  
        writeln('SerialPortNames Init: '+GetSerialPortNames);
        with TBlockSerial.Create do begin
          SetCommState;
          Free;
        end; 
      end; 
      arTimer:= TTimer.Create(Self);
      arTimer.Enabled:= true;
      arTimer.Interval:= 2000;
      arTimer.OnTimer:= @eventActTimer;  
      //ConnectArduinoSense;
      Writeln('Hello Temp/Web server start at: '+sr);
      ShowMessageBig('maXbox HellTempWeb server at: '+sr+':'+itoa(IPPORT)+#1310+
                          '  Press OK to quit webserver!'+#13);
    finally
      writeln('SocketServer stop: '+timetoStr(now)); //Destroy;
      Active:= False; Free;
      hlog1.Add('<<<< Stop socktimer {App_name}{40@}{now}');
      hlog1.Free;
      arTimer.enabled:= false;
      arTimer.Free;
    end;
  end;
End.


Ref:
  https://rosettacode.org/wiki/Hello_world/Web_server#Delphi
  add bindings & contenttype for more convention
  SetCommState;
   //'<br />URI: ' + ARequestInfo.params[1] +
   
  To Do Task: 
  - log the exceptions
  - reduce latency with open comport
  - fix the host start time
  
  Exception: Could not bind socket. Address and port are already in use.
   PrintF('Command %s received: %s of temperature C°: %s',
           [RequestInfo.Command,thread.connection.Socket.binding.PeerIP,tmp2]);
 
Doc:
   Function DateTimeToInternetStr( const Value : TDateTime; const AIsGMT : Boolean) : String
   Function GetIPAddress( const HostName : string) : string
   Function GetIP( const HostName : string) : string
   Function GetIPHostByName(const AComputerName: String): String;
   function GetIPFromHost(const HostName: string): string;

   HTTPServer1.Bindings.Add.IP := '127.0.0.1';
   HTTPServer1.Bindings.Add.Port := 50001;
   
  writeln(GetIPAddress(getHostName));
  writeln(GetIP(getHostName));
  writeln(GetIPHostByName(gethostname));
  writeln(GetIPfromhost(gethostname));
  
   //writeln(RecvBlock(1000))
      //SendString('8')
     
This is a common newbie mistake. You are creating two bindings, one bound to 127.0.0.1:DefaultPort, and one bound to 0.0.0.0:50001. You need one binding instead, that is bound to 127.0.0.1:50001 instead.

with HTTPServer1.Bindings.Add do begin
  IP := '127.0.0.1';
  Port := 50001;
end;

client call example:

procedure TDataFormbtnHTTPSendGetClick(Sender: TObject);
var
  HTTPClient : TIdHTTP;
  responseStream : TMemoryStream;
begin
  HTTPClient := TIdHTTP.Create(Nil);
  responseStream := TMemoryStream.Create;
  try
    try
      HTTPClient.Get1('http://127.0.0.1:8080', responseStream);
      responseStream.Seek(0, soFromBeginning);
      SetLength(Sr, responseStream.Size);
      responseStream.Read(Sr, responseStream.Size);
      writeln('response: '+sr)
      //writeln(': '+streamtoString3(responseStream))
    except 
      //on e : Exception do begin
      showmessage('Could not send get request to localhost, port 8080');
    end;
    //end;
  finally
    //FreeAndNil(HTTPClient);
    HTTPClient.Free;
    HTTPClient:= Nil;
    responseStream.Free;
  end;
end;

//******************************Arduino Uno************************
int incomingByte = 0;
int gndPin = A1;    // select the input pin for the potentiometer
int sensePin = 2;   //analog in
int ledPin = 13;      // select the pin for the LED
int plusPin = A3;  // variable to store the value coming from the sensor
int cnt = 0;
int ledPin8 = 8; 
int val = 0;   

 void setup(){
   Serial.begin(9600);
     pinMode(ledPin8,OUTPUT);    // declare the LED's pin as output 
  pinMode(gndPin, OUTPUT);  
  digitalWrite(gndPin, LOW);
  pinMode(plusPin, OUTPUT);  
  digitalWrite(plusPin, HIGH);
  //Serial.begin(9600);
  pinMode(13, OUTPUT);
 }

 void loop(){
   //data=analogRead(rfReceivePin);    //listen for data on Analog pin 0
   /*if (Serial.available() > 0) {
     incomingByte = Serial.read();
     Serial.println(incomingByte, DEC);
   }*/
   incomingByte = 0;
 int raw = analogRead(sensePin);   
  float volts = raw / 205.0;
  float tempC = 100.0 * volts - 50;
  float tempF = tempC * 9.0/5.0+32.0;
  Serial.print(cnt); 
  //Serial.print(DateTimeStrings());      
  Serial.print(" C.temp: ");
  Serial.println(tempC); 
  // turn the ledPin on
  val = Serial.read();      // read the serial port 
    if (val=='8'){
      digitalWrite(ledPin8,HIGH); 
    }
    if (val=='H'){
      digitalWrite(ledPin8,LOW); 
    }
  //if (timeStatus()!= timeNotSet) {
    //digitalClockDisplay();  
  //delay(1000);
  //digitalClockDisplay(); 
  
  
 
  delay(1000);  
 }


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