Using UPD to find IP addresses for a TCP network in 5 parts.

Posted on Sun 2nd, October 2016

• #1

Setup a TCP network server
Setup a TCP client
Modify ESP8266WiFi_0v25.js to do UDP and TCP
Use UDP to allow clients to find the server IP address
The UDP/TCP client.
Setup a TCP network server
The TCP server and client code are based on the examples listed under the Sockets section of
http://www.espruino.com/Internet
The following code sets up a TCP server on port 9988.
You will need to edit:
//var Hardware=0; //Espruino board
var Hardware =1; //PICO
var SSID="ssid";
var key= "router passcode";

When a client connects two commands are accepted “LED On” and “LED Off”

//netServer3.js
//2 Oct 2016
//espruino board with ESP8266
//PICO  with ESP8266
var Sport=9988;
//var Hardware=0; //Espruino board
var Hardware =1; //PICO
var SSID="ssid";
var key= "router passcode";
var Serial;
var MyIP="";
function test(){
if(Hardware===1)Serial=Serial2;
if(Hardware===0)Serial=Serial4;

if(Hardware===1){
 digitalWrite(B9,1); // enable on Pico Shim V2
 Serial.setup(115200, { rx: A3, tx : A2 }); //Pico
}
if(Hardware===0)Serial.setup(115200, { rx: C11, tx : C10 }); 
//espruino board

console.log("Start connection process");
var wifi = require("ESP8266WiFi_0v25").connect(Serial, function(err) {
  if (err)return 1;// throw err;
console.log("Reset the ESP8266");
  wifi.reset(function(err) {
    if (err)return 1;// throw err;
    console.log("Connecting to WiFi");
    wifi.connect(SSID,key, function(err) {
      if (err)return 1;//throw err;
      wifi.getIP(function(l,ip){console.log("IP= ",ip,"\n\r"+l);MyIP=ip;
      console.log("Wi-Fi Connected");
// Now you can do something, 
serve();

////////////////////////////////////////////////////////////
     });
    });
  });
});
}//end test

var x;
console.log("Start");
x=test();
if(x!==0)console.log("Try again");//error seen

if(x===0) console.log("Exit Seen");

//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
function serve(){
 var data;
 var server = require("net").createServer(function(c) {
  // A new client has connected
//  c.write("Hello");
/*  c.on('data', function(data) {
    console.log(">"+JSON.stringify(data));
  });
*/
   c.on('close',function(d){
   console.log("Close "+d);
   data=c.read(c.available());
   console.log(data);
   c.write(data);
     if(data==="LED Off"){
      digitalWrite(B12,0); //B12 is green LED
     }
     if(data==="LED On"){
      digitalWrite(B12,1);
     }
  });
  c.end();
});
server.listen(Sport);

}

The TCP server output:

>echo(0);
Start
Start connection process
Try again
=undefined
Reset the ESP8266
Connecting to WiFi
IP=  192.168.1.3
null
Wi-Fi Connected
>

At this point I disconnect the WebIDE from the TCP server hardware and reconnect using putty.
Make a note of the server IP addess.

1 Attachment

netServer3.js

• #2

ClearMemory041063

Setup a TCP client
This code sets up the TCP client on port 9988.
The console is redirected to the Loopback to allow the WebIDE to act as a simple menu system.
You will need to edit the hardware flag , ssid and router passcode.
Additionally you have to hardcode the IP address of the server. (we will fix this with UDP later)

//netclient3.js
//2 Oct 2016
//espruino board with ESP8266
//PICO  with ESP8266
var IP="192.168.1.3";
var Sport=9988;
//var Hardware=0; //Espruino board
var Hardware =1; //PICO
var SSID="ssid";
var key= "router passcode";
var Serial;
function test(){
if(Hardware===1)Serial=Serial2;
if(Hardware===0)Serial=Serial4;
if(Hardware===1){
digitalWrite(B9,1); // enable on Pico Shim V2
Serial.setup(115200, { rx: A3, tx : A2 }); //Pico
}
if(Hardware===0)Serial.setup(115200, { rx: C11, tx : C10 }); 
//espruino board
console.log("Start connection process");
var wifi = require("ESP8266WiFi_0v25").connect(Serial, function(err) {
if (err)return 1;// throw err;
console.log("Reset the ESP8266");
wifi.reset(function(err) {
if (err)return 1;// throw err;
console.log("Connecting to WiFi");
wifi.connect(SSID,key, function(err) {
  if (err)return 1;//throw err;
  wifi.getIP(function(l,ip){console.log("IP= ",ip,"\n\r"+l);});
  console.log("Wi-Fi Connected");
// Now you can do something,
menu();
////////////////////////////////////////////////////////////
});
});
});
}//end test
//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
function sendit(msg){
var reply="";
var client = require("net").connect({host: IP, port: Sport}, function() {
//  console.log('client connected');
client.write(msg);
client.on('data', function(data) {
reply+=data;
console.log(">"+JSON.stringify(data));
});
client.on('end', function() {
//    console.log('client disconnected');
return reply;
});
});
}

////////////////////////////////////////////////////////////////////////
var sst="";
//Menus
menu=function(){
USB.print(" \n\r");
USB.print("Select using digit and return key\n\r");
USB.print("1 LED Off\n\r");
USB.print("2 LED On\n\r");
USB.print("0 Exit\n\r");
};
parsecmd=function(){
USB.print("\n\r");
switch(this.sst.charAt(0)){
case "1"://LED off
 sst="";
 USB.print("LED Off\n\r");
 sendit("LED Off");
break;
case "2"://LED On
 USB.print("LED On\n\r");
 sst="";
 sendit("LED On");
break;
case"0"://Exit
 LoopbackA.print("USB.setConsole();\n\r");
 sst="";
 USB.print("Exit\n\r");
break;
default:
 menu();
break;
}//end switch sst
};//end parsecmd
//input cmd from terminal,send it to parsecmd()
USB.on('data', function (data) {
var i;
sst+=data;
USB.print(data);
if(sst.length>0)
if(sst.charAt(sst.length-1)==="\r")parsecmd();
});
//Espruino replies here
LoopbackA.on('data',function(data){
USB.print(data); //sending data to terminal
});
/////////////////////////
setTimeout(function () {
var x;
console.log("Start");
LoopbackB.setConsole();
x=test();
if(x!==0)console.log("Try again");//error seen
if(x===0) console.log("Exit Seen");
}, 1000);

And the WebIde output:

>echo(0);
=undefined
Start
-> LoopbackB
<- USB
Start connection process
Try again
Reset the ESP8266
Connecting to WiFi
>
Select using digit and return key
1 LED Off
2 LED On
0 Exit
Wi-Fi Connected
IP=  192.168.1.4
null
>1
LED Off
2
LED On
1
LED Off
0
Exit
<- LoopbackB
=undefined
=undefined
>USB.setConsole();
-> USB

Notice that the 0 Exit restores the console to the USB port.
The Server output on the Putty terminal:

Close false
LED Off
Close false
LED On
Close false
LED Off
>

1 Attachment

netClient3.js

• #3

ClearMemory041063
1. Modify ESP8266WiFi_0v25.js to do UDP and TCP
  Add UDPflag and CIPstartSTR.
```
var at;
var UDPflag=0;
var CIPstartStr="";
var socks = [];
```
Modify the code to CIPstart a client in the create: function
```
  create : function(host, port) {
    /* Create a socket and return its index, host is a string, port is an integer.
    If host isn't defined, create a server socket */  
    if (host===undefined) {
console.log("Server");
      sckt = MAXSOCKETS;
      socks[sckt] = "Wait";
      sockData[sckt] = "";
      at.cmd("AT+CIPSERVER=1,"+port+"\r\n", 10000, function(d) {
        if (d=="OK") {
          socks[sckt] = true;
        } else {
          socks[sckt] = undefined;
          setTimeout(function() {
            throw new Error("CIPSERVER failed ("+(d?d:"Timeout")+")");
          }, 0);
        }
      });
      return MAXSOCKETS;
    } else {  
console.log("Client");
      var sckt = 0;
      while (socks[sckt]!==undefined) sckt++; // find free socket
      if (sckt>=MAXSOCKETS) throw new Error("No free sockets");
      socks[sckt] = "Wait";
      sockData[sckt] = "";

if(UDPflag){//UDP client
 CIPstartStr='AT+CIPSTART='+sckt+',"UDP",'+JSON.stringify(host)+','+port+','+port+',0\r\n';

}else{//TCP client
 CIPstartStr='AT+CIPSTART='+sckt+',"TCP",'+JSON.stringify(host)+','+port+'\r\n';
}//end else
at.cmd(CIPstartStr,10000, function cb(d) {
```
Add code to set and reset the UDP flag
```
"SetUDP":function(){ UDPflag=1;
},
"SetTCP" : function(){ UDPflag=0;
},

  "getIP" : function(callback) {
```
UDP.js placed in modules directory of WebIDE project.

AT commands for UDP
https://github.com/espressif/ESP8266_AT/wiki/at_example_0020000903
https://gist.github.com/mokogobo/3f4d2f074305d4d84344

https://cdn.sparkfun.com/assets/learn_tutorials/4/0/3/4A-ESP8266__AT_Instruction_Set__EN_v0.30.pdf
AT+CIPSTART – Establish TCP connection or register UDP port, start connection
Example
AT+CIPSTART="TCP","192.168.101.110",1000
Single connection
(+CIPMUX=0)
AT+CIPSTART=,,[,,]
[,]
Multiple connection
(+CIPMUX=1)
AT+CIPSTART=,,,[,,]
[,]
Response
OK
or
ERROR
If connection already exists, returns
ALREAY CONNECT
Parameters

ID of the connection (0~4), for multi-connect

string, "TCP" or "UDP"

string, remote IP

string, remote port
[]
for UDP only
[] In UDP transparent transmission, it has to be 0.
[] 0
: destination peer entity of UDP will not change.
[] 1
: destination peer entity of UDP can change once.
[] 2
: destination peer entity of UDP is allowed to change.
Note: [] can only be used when [] is set.
[]
default 0. unit: 500 milliseconds.
[] 0
: disable TCP keep-alive
[] 1 ~ 7200
: TCP keep-alive interval

AT+CIPSTART – Function 2: R
egister UDP port
Example
AT+CIPSTART="UDP", "192.168.101.110", 1000, 1002,
2
Single connection
(AT
+CIPMUX=0)
AT+CIPSTART=, , [, ,
]
Multiple connection
(AT+CIPMUX=1
)
AT+CIPSTART=, , , [, , ]
Response
OK or
ERROR
If connection already exists, returns
ALREADY CONNECT

1 Attachment
- UDP.js

• #4

ClearMemory041063

Use UDP to allow clients to find the server IP address
The UDP is used with a broadcast IP to allow a named client to locate a named server’s IP address.
The message sent via UDP:
```
function UDPmsg(a,b,c,d){
this.ClientName=a;
this.ClientIP=b;
this.ServerName=c;
this.ServerIP=d;
}
var UDP1=new UDPmsg("Bob",0,"Bill",0);
```

Client named Bob will ask server named Bill for Bill’s IP address

The server code:

//UDP_TCPserver1.js
//2 Oct 2016
//espruino board with ESP8266
//PICO  with ESP8266
//var BroadIP="255.255.255.255";
var BroadIP="192.168.1.255";
//var Hardware=0; //Espruino board
var Hardware =1; //PICO
var SSID="ssid";
var key= "router passcode";
var Serial;
var Wifi;
//var LocalIP;
var UDPport=1234;
var TCPport=9988;
function UDPmsg(a,b,c,d){
 this.ClientName=a;
 this.ClientIP=b;
 this.ServerName=c;
 this.ServerIP=d;
}
var UDP1=new UDPmsg("Bob",0,"Bill",0);
var UDP2=new UDPmsg("",0,"",0);
var ddata="";
function test(){
if(Hardware===1)Serial=Serial2;
if(Hardware===0)Serial=Serial4;

if(Hardware===1){
 digitalWrite(B9,1); // enable on Pico Shim V2
 Serial.setup(115200, { rx: A3, tx : A2 }); //Pico
}
if(Hardware===0)Serial.setup(115200, { rx: C11, tx : C10 }); 
//espruino board

console.log("Start connection process");
var wifi = require("UDP").connect(Serial, function(err) {
//var wifi = require("ESP8266WiFi_0v25").connect(Serial, function(err) {
  if (err)return 1;// throw err;
  Wifi=wifi;
console.log("Reset the ESP8266");
  wifi.reset(function(err) {
    if (err)return 1;// throw err;
Wifi.at.cmd("AT+CWMODE_CUR=3\r\n", 1000, function(d){console.log(d+"xx1");});
Wifi.at.cmd("AT+CIPMUX=1\r\n", 1000, function(d){console.log(d+"xx2");});
 console.log("Connecting to WiFi");
 wifi.connect(SSID,key, function(err) {
  if (err)return 1;//throw err;
  wifi.getIP(function(l,ip){
   console.log("IP= ",ip,"\n\r");
   UDP1.ServerIP=ip;
   console.log("LocalIP= ",UDP1.ServerIP);
   console.log("WiFi Connected ");

//start the UDP listener
   setupUDP(); 
//HTTP or Network Server goes here
   TCPserve();

////////////////////////////////////////////////////////////
     });//end wifi.getIP
    });//end wifi.connectSSID
  });//end wifi.reset
});//end wifi.connect
}//end test

function setupUDP(){
    Wifi.SetUDP();
  var client = require("net").connect({host:BroadIP,port:UDPport ,protocolVersion: 17}, function() {
    console.log('client connected');
    client.write(JSON.stringify(UDP1));
    client.on('data', function(data){
     ddata+=data;
     if(ddata.charAt(ddata.length-1)==='}'){
      UDP2=JSON.parse(ddata);
      console.log(">"+ddata);
      if(UDP1.ServerName===UDP2.ServerName){
       UDP2.ServerIP=UDP1.ServerIP;
       client.write(JSON.stringify(UDP2));
       ddata="";
      }//endif
     }//endif
    });//end client on data
    client.on('close',function(){console.log("client Close");});
    client.on('end', function() {
     console.log('client disconnected');
    });//end client on end
    //client.end();
   });//end UDP client connect
}//end setupUDP

function TCPserve(){
 var data;
 Wifi.SetTCP();
 var server = require("net").createServer(function(c) {
  // A new client as connected
//  c.write("Hello");
/*  c.on('data', function(data) {
    console.log(">"+JSON.stringify(data));
  });
*/
   c.on('close',function(d){
   console.log("Close "+d);
   data=c.read(c.available());
   console.log(data);
   c.write(data);
     if(data==="LED Off"){
      digitalWrite(B12,0); //B12 is green LED
     }
     if(data==="LED On"){
      digitalWrite(B12,1);
     }
  });
  c.end();
});
server.listen(TCPport);
}//end TCPserve

var x;
console.log("Start");
x=test();
if(x!==0)console.log("Try again");//error seen

if(x===0) console.log("Exit Seen");

The output as the server starts

>echo(0);
Start
Start connection process
Try again
=undefined
Reset the ESP8266
Connecting to WiFi
OKxx1
OKxx2
IP=  192.168.1.3
LocalIP=  192.168.1.3
WiFi Connected
Client
Server
client connected
Send 0 {"ClientName":"Bob","ClientIP":0,"ServerName":"Bill","ServerIP":"192.168.1.3"}
>

Again disconnect the server from WebIde and connect to Putty terminal application.

1 Attachment

UDP_TCPserver1.js

• #5

ClearMemory041063

The UDP/TCP client

//UDP_TCPclient1.js
//2 Oct 2016
//espruino board with ESP8266
//PICO  with ESP8266
//var BroadIP="255.255.255.255";
var BroadIP="192.168.1.255";
//var LocalIP;
var UDPport=1234;
var TCPport=9988;
//var Hardware=0; //Espruino board
var Hardware =1; //PICO
var SSID="ssid";
var key= "router passcode";
var Serial;
var Wifi;
function UDPmsg(a,b,c,d){
this.ClientName=a;
this.ClientIP=b;
this.ServerName=c;
this.ServerIP=d;
}
var UDP1=new UDPmsg("Bob",0,"Bill",0);
var UDP2;//=new UDPmsg("",0,"",0);
var ServerIP=0;
var ddata="";
function test(){
if(Hardware===1)Serial=Serial2;
if(Hardware===0)Serial=Serial4;
if(Hardware===1){
digitalWrite(B9,1); // enable on Pico Shim V2
Serial.setup(115200, { rx: A3, tx : A2 }); //Pico
}
if(Hardware===0)Serial.setup(115200, { rx: C11, tx : C10 }); 
//espruino board
console.log("Start connection process");
var wifi = require("UDP").connect(Serial, function(err) {
if (err)return 1;// throw err;
Wifi=wifi;
console.log("Reset the ESP8266");
wifi.reset(function(err) {
if (err)return 1;// throw err;
Wifi.at.cmd("AT+CWMODE_CUR=3\r\n", 1000, function(d){console.log(d+"xx1");});
Wifi.at.cmd("AT+CIPMUX=1\r\n", 1000, function(d){console.log(d+"xx2");});
console.log("Connecting to WiFi");
wifi.connect(SSID,key, function(err) {
if (err)return 1;//throw err;
wifi.getIP(function(l,ip){console.log("IP= ",ip,"\n\r");
 UDP1.ClientIP=ip;
 console.log("Wi-Fi Connected");
// Setup UDP Client 
 wifi.SetUDP();
 var client = require("net").connect({host: BroadIP, port: UDPport,protocolVersion: 17}, function() {
  console.log('client connected');
  console.log(UDP1.ClientIP);
  client.write(JSON.stringify(UDP1));
  client.on('data', function(data) {
   ddata+=data;
    if(ddata.charAt(ddata.length-1)==='}'){
     UDP2=JSON.parse(ddata);
     console.log(">"+ddata);
     ddata="";
      if((UDP1.ClientName===UDP2.ClientName)&&       (UDP1.ServerName===UDP2.ServerName)){
       ServerIP=UDP2.ServerIP;
//HTTP or network client goes here
       menu();
      }else{
      }//endif
    }//endif ddata=}
  });//end client on data
  client.on('end', function() {
   console.log('client disconnected');
  });//client on end
  //client.end(");
 });//end client.net
});//end wif.getIP
////////////////////////////////////////////////////////////
});//end wifi.connect SSID
});//end wifi.reset
});//end wifi.connect serial
}//end test
//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
function sendit(msg){
var reply="";
Wifi.SetTCP();
var client = require("net").connect({host: ServerIP, port: TCPport}, function() {
//  console.log('client connected');
client.write(msg);
client.on('data', function(data) {
reply+=data;
console.log(">"+JSON.stringify(data));
});
client.on('end', function() {
//    console.log('client disconnected');
return reply;
});
});
}
////////////////////////////////////////////////////////////////////////
var sst="";
//Menus
menu=function(){
USB.print(" \n\r");
USB.print("Select using digit and return key\n\r");
USB.print("1 LED Off\n\r");
USB.print("2 LED On\n\r");
USB.print("0 Exit\n\r");
};
parsecmd=function(){
USB.print("\n\r");
switch(this.sst.charAt(0)){
case "1"://LED off
 sst="";
 USB.print("LED Off\n\r");
 sendit("LED Off");
break;
case "2"://LED On
 USB.print("LED On\n\r");
 sst="";
 sendit("LED On");
break;
case"0"://Exit
 LoopbackA.print("USB.setConsole();\n\r");
 sst="";
 USB.print("Exit\n\r");
break;
default:
 menu();
break;
}//end switch sst
};//end parsecmd
//input cmd from terminal,send it to parsecmd()
USB.on('data', function (data) {
var i;
sst+=data;
USB.print(data);
if(sst.length>0)
if(sst.charAt(sst.length-1)==="\r")parsecmd();
});
//Espruino replies here
LoopbackA.on('data',function(data){
USB.print(data); //sending data to terminal
});
/////////////////////////
setTimeout(function () {
var x;
console.log("Start");
LoopbackB.setConsole();
x=test();
if(x!==0)console.log("Try again");//error seen
if(x===0) console.log("Exit Seen");
}, 1000);

The WebIde screen:

>echo(0);
=undefined
Start
-> LoopbackB
<- USB
Start connection process
Try again
Reset the ESP8266
Connecting to WiFi
OKxx1
OKxx2
IP=  192.168.1.4
Wi-Fi Connected
Client
client connected
192.168.1.4
Send 0 {"ClientName":"Bob","ClientIP":"192.168.1.4","ServerName":"Bill","ServerIP":0}
>
Select using digit and return key
1 LED Off
2 LED On
0 Exit
>{"ClientName":"Bob","ClientIP":"192.168.1.4","ServerName":"Bill","ServerIP":"192.168.1.3"}
>1
LED Off
Client
Send 1 LED Off
>2
LED On
Client
Send 1 LED On
>0
Exit
<- LoopbackB
=undefined
=undefined
>USB.setConsole();
-> USB

And the server screen:

>{"ClientName":"Bob","ClientIP":"192.168.1.4","ServerName":"Bill","ServerIP":0}
Send 0 {"ClientName":"Bob","ClientIP":"192.168.1.4","ServerName":"Bill","ServerIP":"192.168.1.3"}
Socket accept 1 "LED O" undefined
Close false
LED O
Socket accept 1 "ff" undefined
Close false
ff
Socket accept 1 "LED On" undefined
Close false
LED On
>

1 Attachment

UDP_TCPserver1.js

• #6

dh.

I was trying your code, but the net module isn't available anymore on http://www.espruino.com/modules/. Is there anything I'm missing here?
• #7

ClearMemory041063

The code you are trying to load is for either an espruino board or Pico connected via serial port to an ESP8266. It doesn't currently work on an ESP8266 flashed with the Espruino firmware. That would require modification to the Espruino source code and a recompile. As a consumer of Espruino I'm not currently setup to do such a task. Perhaps some of the ESP8266 folks on the Forum who are so equipped can comment further.

Some modules are built into the firmware and aren't listed in the modules on the Espruino site.

Which hardware combination are you trying to use?
• #8

allObjects
Espruino looks at different places for modules at code upload time when using just the name as string literal (single or double quoted, but not as variable):
1. built in - no upload needed. For access, you still need to require() the module
2. http://www.espruino.com/modules/ - from Espruino's official modules repository
3. modules folder from project sandbox folder specified
Web IDE code upload can also handle a url in (as string literal): the code will be pulled from the given url and uploaded to Espruino board (board with Espruino firmware / standalone operating system).

Espruino executes the uploaded code - it is JavaScript after all - and stores the result in the modules cache, from where it is then pulled at runtime when the require() is actually executed. Again, at that moment it checks wether it is a (binary / firmware / operating system) built-in module, a cached module, or it can be found on a mounted SD card / file system. At runtime / on execution, require() does not care if the provided string argument is a literal or a variable. This allows to dynamically require a module at runtime by a variable, but as said, the module has to found, otherwise an error / exception is thrown.

To make the code example to work, it may be good enough to define the sandbox project modules folder in the Web IDE and save the UDP module as UDP.js (or minified as UDP.min.js) in that folder. Minifying can be done on googles (JS) closure compiler Web page.

For a bit more what is going on uploading code, saving code on Espruino board, repowering Espruino boards, etc. can found in the conversation titled simple explanation how to save code that espruino run on start?.

I hope this helps getting you going...

Post a reply
- Bold
- Italics
- Link
- Image
- List
- Quote
- code
- Preview
Formatting Help

Don't worry about formatting, just type in the text and we'll take care of making sense of it. We will auto-convert links, and if you put asterisks around words we will make them bold.

Tips:

Create headers by underlining text with ==== or ----

To *italicise* text put one asterisk each side of the word

To **bold** text put two asterisks each side of the word

Embed images by entering:
![](https://www.google.co.uk/images/srpr/logo4w.png)
That's the hard one: exclamation, square brackets and then the URL to the image in brackets.

* Create lists by starting lines with asterisks

1. Create numbered lists by starting lines with a number and a dot

> Quote text by starting lines with >

Mention another user by @username

For syntax highlighting, surround the code block with three backticks:

```
Your code goes here
```
Just like Github, a blank line must precede a code block.

If you upload more than 5 files we will display all attachments as thumbnails.

For a full reference visit the Markdown syntax.

Using UPD to find IP addresses for a TCP network in 5 parts.

About