Folks:

There's been some recent interest in the Telnet server sketch I created a couple years back.  The Telnet server allows all Arduino control pins to be read or written using a simple command line protocol.  Once you've loaded the sketch, you should be able to Telnet into the Arduino's IP address, get a prompt, and type ? <cr> for help. 

The code on the old forum was developed in Arduino environment 0.23 and no longer compiles without edits.  I'm posting the updated code here:  http://dl.dropbox.com/u/47320696/ArduinoTelnetServer.zip.

I hope this helps; drop me a note if you find it useful.

Best Regards,

stlentz [at] gmail [dot] com

Pepitovadecurt:

You should be able to write a short function that gets a user name and password and checks them against known values, then call this function right after the client connects.  Go to the resources section on the arduino website and review the Ethernet library functions and text functions.  Give this a try and if you get stuck, let me know, I can try to put something together over the weekend.

I thought about putting this in but  the Arduino Ethernet functions are so basic, the username and password would be sent in the clear,  there's really not much security benefit.  

OK, I understand, but there's nothing in the code that should make this happen.  I guess you will need to try writing a different sketch to find out if it is my code or something else.  I tried with my board and I can set all ten pins high and dr says they are all high.  Sorry I can't be more help.

-Steve

That's weird - I just checked it and it's working for me.  Pin 0 always starts out high, but you can set it low, so that seems normal.  

Is pin 7 the only one affected?  Can you read pin 7 with a voltmeter or connect an LED to see what is really happening? I assume you have nothing connected that could be pulling it low.  There is mention in the Arduino instructions about pins sometimes going bad on the ATMega chip itself; I hope that isn't the case here.

-Steve

Pins 10-13 are used to communicate with the Ethernet shield.  Since they can't be used for any other purpose, there is no reason to read them.

Hope this answers your question.

Rgds,
Steve

Here is the last bit of code, you need both to make the sketch work!

Code:

void setPinMode()
  // if we got here, textBuff[0] = 'p'
{
  int pin = -1;
  int pinModeSetting = -1;
  if (textBuff[1] == 'm' && textBuff[3] == '=' && textBuff[6] == 0x0d) {
        //if yes, get the pin number, setting, and set the pin
        pin = parseDigit(textBuff[2]);
        pinModeSetting = parseModeSetting();
        if(pin > -1 && pinModeSetting == 0) {
          pinMode(pin, OUTPUT);
          client.println("OK");
        }
        if(pin > -1 && pinModeSetting == 1) {
          pinMode(pin, INPUT);
          client.println("OK");
        }
        if(pin < 0 || pinModeSetting < 0) printErrorMessage();
      }
   else printErrorMessage();
}


int parseModeSetting()
//look in the text buffer to find the pin setting
//return -1 if not valid
{
  int pinSetting = -1;
  if(textBuff[4] == 'o' && textBuff[5] == 'u') pinSetting = 0;
  if(textBuff[4] == 'i' && textBuff[5] == 'n') pinSetting = 1;
  return pinSetting;
}


int parseDigit(char c)
{
  int digit = -1;
  digit = (int) c - 0x30; // subtracting 0x30 from ASCII code gives value
  if(digit < 0 || digit > 9) digit = -1;
  return digit;
}


void printErrorMessage()
{
  client.println("Unrecognized command.  ? for help.");
}


void checkCloseConnection()
  // if we got here, textBuff[0] = 'c', check the next two
  // characters to make sure the command is valid
{
  if (textBuff[1] == 'l' && textBuff[2] == 0x0d)
    closeConnection();
  else
    printErrorMessage();
}


void closeConnection()
{
  client.println("\nBye.\n");
  client.stop();
  connectFlag = 0;
}


void printHelpMessage()
{
  client.println("\nExamples of supported commands:\n");
  client.println("  dr       -digital read:   returns state of digital pins 0 to 9");
  client.println("  dr4      -digital read:   returns state of pin 4 only");
  client.println("  ar       -analog read:    returns all analog inputs");
  client.println("  dw0=hi   -digital write:  turn pin 0 on  valid pins are 0 to 9");
  client.println("  dw0=lo   -digital write:  turn pin 0 off valid pins are 0 to 9");
  client.println("  aw3=222  -analog write:   set digital pin 3 to PWM value 222");
  client.println("                              allowed pins are 3,5,6,9");
  client.println("                              allowed PWM range 0 to 255");
  client.println("  pm0=in   -pin mode:       set pin 0 to INPUT  valid pins are 0 to 9");
  client.println("  pm0=ou   -pin mode:       set pin 0 to OUTPUT valid pins are 0 to 9");
  client.println("  cl       -close connection");
  client.println("  ?        -print this help message");
}

 

I'm reposting the original message as I (stupidly) left my e-mail in the code.  Hopefully not too many crawlers have picked it up.

Here's something that might help someone out there.  There are plenty of examples of web servers and even a few web services interfaces, but few if any command line interfaces.  A few old forum posts seem to be looking for this, but I haven't found any good examples.  This sketch allows you to read all digital and analog pins, set digital outputs high or low, set PWM outputs and change the mode of digital pins.  This could be useful when debugging hardware or perhaps you just have a hankering for good old text based interaction.  I've keep the command structure very simple, for example analogRead is abbreviated as ar, in an effort to keep the sketch size small and so the code will run reasonably fast.  There's built in help, so once the sketch is running you can ask it to give you a complete list of supported commands.  Please post comments here if you find this useful (or not) or have any other suggestions.

The code is too long for one forum message, so you must cut and paste it from this message and the following message.

Code:

/*                             *
 *  Arduino Telnet Server      *
 *      7 July 2010            *
 *   Basic Arduino I/O via     *
 *  a command line interface   *
 *      by Steve Lentz         *
 * stlentz[at]gmail[dot]com   *

 Quick Start Instructions:
 1) Set Ethernet address in code below.
 2) Compile and upload sketch.
 3) Connect Arduino to Ethernet.
    Make sure link light is on.
 4) Telnet to Arduino's IP.
 5) On some Telnet clients, hit return to wake up connection.
 6) When connected, type ? <cr> for help.  
 7) Try a simple command such as 'ar'.

Other notes
Tested on Duemilanove with Ethernet Shield.  
Should work on compatible boards.
Tested with Win XP, OS X, and Debian Telnet clients.  
Compiles to about 9 KB, can be made smaller by removing
  unneeded commands, help message, etc.
I am an entirely self-taught C programmer; if you
  don't like my code, too bad ;-).  */


// Ethernet parameters
#include <Ethernet.h>

byte mac[] =     { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
byte ip[]  =     {192, 168, 1, 7 };
byte gateway[] = {192, 168, 1, 1 };
byte subnet[]  = {255, 255, 255, 0 };

// Other global variables
#define textBuffSize 9 //length of longest command string plus two spaces for CR + LF
char textBuff[textBuffSize]; //someplace to put received text
int charsReceived = 0;

boolean connectFlag = 0; //we'll use a flag separate from client.connected
                         //so we can recognize when a new connection has been created
unsigned long timeOfLastActivity; //time in milliseconds of last activity
unsigned long allowedConnectTime = 300000; //five minutes

Server server(23); // Telnet listens on port 23
Client client = 0; // Client needs to have global scope so it can be called
                   // from functions outside of loop, but we don't know
                   // what client is yet, so creating an empty object

void setup()
{
  // setting pins 0 to 9 as outputs
  // pins 10-13 are used by the Ethernet Shield
  for(int  i= 0; i < 10; i++)  pinMode(i, OUTPUT);

  Ethernet.begin(mac, ip, gateway, subnet);
  server.begin();
}

void loop()
{
  // look to see if a new connection is created,
  // print welcome message, set connected flag
  if (server.available() && !connectFlag) {
    connectFlag = 1;
    client = server.available();
    client.println("\nSteve's Arduino Telnet Server");
    client.println("? for help");
    printPrompt();
  }
  
  // check to see if text received
  if (client.connected() && client.available()) getReceivedText();
    
  // check to see if connection has timed out
  if(connectFlag) checkConnectionTimeout();

// code to do other things in loop would go here

}


void printPrompt()
{
  timeOfLastActivity = millis();
  client.flush();
  charsReceived = 0; //count of characters received
  client.print("\n>");
}


void checkConnectionTimeout()
{
  if(millis() - timeOfLastActivity > allowedConnectTime) {
    client.println();
    client.println("Timeout disconnect.");
    client.stop();
    connectFlag = 0;
  }
}


void getReceivedText()
{
  char c;
  int charsWaiting;

  // copy waiting characters into textBuff
  //until textBuff full, CR received, or no more characters
  charsWaiting = client.available();
  do {
    c = client.read();
    textBuff[charsReceived] = c;
    charsReceived++;
    charsWaiting--;
  }
  while(charsReceived <= textBuffSize && c != 0x0d && charsWaiting > 0);
  
  //if CR found go look at received text and execute command
  if(c == 0x0d) {
    parseReceivedText();
    // after completing command, print a new prompt
    printPrompt();
  }
  
  // if textBuff full without reaching a CR, print an error message
  if(charsReceived >= textBuffSize) {
    client.println();
    printErrorMessage();
    printPrompt();
  }
  // if textBuff not full and no CR, do nothing else;  
  // go back to loop until more characters are received
  
}  


void parseReceivedText()
{
  // look at first character and decide what to do
  switch (textBuff[0]) {
    case 'a' : doAnalogCommand();        break;
    case 'd' : doDigitalCommand();       break;
    case 'p' : setPinMode();             break;
    case 'c' : checkCloseConnection();   break;
    case '?' : printHelpMessage();       break;
    case 0x0d :                          break;  //ignore a carriage return
    default: printErrorMessage();        break;
  }
 }


void doDigitalCommand()
  // if we got here, textBuff[0] = 'd'
{
  switch (textBuff[1]) {
    case 'r' : readDigitalPins(); break;
    case 'w' : writeDigitalPin(); break;
    default: printErrorMessage(); break;
  }
}


void readDigitalPins()
  // if we got here, textBuff[0] = 'd' and textBuff[1] = 'r'
{
  int pin;
  if (textBuff[2] == 0x0d) {
  // output the valueof each digital pin
    for (int i = 0; i < 10; i++) outputPinState(i);
  }
  else {
    pin = parseDigit(textBuff[2]);
    if(pin >=0 && pin <=9) outputPinState(pin);
    else printErrorMessage();
  }
}  


void outputPinState(int pin)
{
  client.print("digital pin ");
  client.print(pin);
  client.print(" is ");
  if (digitalRead(pin)) {
    client.println("HIGH");
  }
  else
    client.println("LOW");
}


void writeDigitalPin()
  // if we got here, textBuff[0] = 'd' and textBuff[1] = 'w'
{
  int pin = -1;
  int pinSetting = -1;
  if (textBuff[3] == '=' && textBuff[6] == 0x0d) {
        //if yes, get the pin number, setting, and set the pin
        pin = parseDigit(textBuff[2]);
        pinSetting = parsePinSetting();
        if(pin > -1 && pinSetting == 0) {
          digitalWrite(pin, LOW);
          client.println("OK");
        }
        if(pin > -1 && pinSetting == 1) {
          digitalWrite(pin, HIGH);
          client.println("OK");
        }
        if(pin < 0 || pinSetting < 0) printErrorMessage();
      }
   else printErrorMessage();
}


int parsePinSetting()
//look in the text buffer to find the pin setting
//return -1 if not valid
{
  int pinSetting = -1;
  if(textBuff[4] == 'l' && textBuff[5] == 'o') pinSetting = 0;
  if(textBuff[4] == 'h' && textBuff[5] == 'i') pinSetting = 1;
  return pinSetting;
}


void doAnalogCommand()
  // if we got here, textBuff[0] = 'a'
{
  switch (textBuff[1]) {
    case 'r' : readAnalogPins(); break;
    case 'w' : writeAnalogPin(); break;
    default: printErrorMessage(); break;
  }
}


void readAnalogPins()
  // if we got here, textBuff[0] = 'a' and textBuff[1] = 'r'
  // check textBuff[2] is a CR then
  // output the value of each analog input pin
{
  if(textBuff[2] == 0x0d) {
    for (int i = 0; i < 6; i++) {
      client.print("analog input ");
      client.print(i);
      client.print(" is ");
      client.println(analogRead(i));
    }
  }
  else printErrorMessage();
}


void writeAnalogPin()
  // if we got here, textBuff[0] = 'a' and textBuff[1] = 'w'
{
  int pin = -1;
  int pwmSetting = -1;
   if (textBuff[3] == '=') {
      //if yes, get the pin number, setting, and set the pin
      pin = parseDigit(textBuff[2]);
      if(pin == 3 || pin == 5 || pin == 6 || pin == 9) {
        pwmSetting = parsepwmSetting();
        if(pwmSetting >= 0 && pwmSetting <= 255) {
          analogWrite(pin,pwmSetting);
          client.println("OK");
        }
        else printErrorMessage();
      }
      else printErrorMessage();
    }
   else printErrorMessage();
}


int parsepwmSetting()
{
  int pwmSetting = 0;
  int textPosition = 4;  //start at textBuff[4]
  int digit;
  do {
    digit = parseDigit(textBuff[textPosition]); //look for a digit in textBuff
    if (digit >= 0 && digit <=9) {              //if digit found
      pwmSetting = pwmSetting * 10 + digit;     //shift previous result and add new digit
    }
    else pwmSetting = -1;
    textPosition++;                             //go to the next position in textBuff
  }
  //if not at end of textBuff and not found a CR and not had an error, keep going
  while(textPosition < 7 && textBuff[textPosition] != 0x0d && pwmSetting > -1);
   //if value is not followed by a CR, return an error
  if(textBuff[textPosition] != 0x0d) pwmSetting = -1;  
  return pwmSetting;
}