Reading incoming char on telnet, concat to a string , then print when delimited

Projects Programming
1

I am having trouble with what should be a very simple task:
-listen on telnet port for incoming characters
-concatenate incoming characters to a string until the ";" character is typed
-print fully concatenated string

I can't figure out how I can concatenate to a string. All that prints is ";", no concat is taking place. Any help would be appreciated. See code below:

void loop() {
  String printString;
  // wait for a new client:
  EthernetClient client = server.available();

  // when the client sends the first byte, say hello:
  if (client) {
    if (!alreadyConnected) {
      // clear out the input buffer:
      client.flush();
      Serial.println("We have a new client");
      
      client.println("Hello, client!");
      alreadyConnected = true;
    }

    if (client.available() > 0) {
      // read the bytes incoming from the client:
      char thisChar = client.read();

      // echo the bytes back to the client:
      server.write(thisChar);
      // echo the bytes to the server as well:


      printString =  printString + thisChar;

    }

  }
  if (printString.endsWith(";")) {

   
    Serial.print(printString);


    printString = "";//clear the string
 

  }
}
2

You are reading only one character. The client send will come in a packet with possibly the entire message.

// change this
    if (client.available() > 0) {
// to this
    while (client.available() > 0) {

That code is more for a chat server. One client sends, and it echoes to all connected clients. Is that what you want? I have code in the playground that works more like a telnet server. It is a bit more complex though. The client doesn't need to send anything for the server to send a "hello" message to the client. Just a thought...
http://playground.arduino.cc/Code/Telnet

3

Thanks for the fast reply. I am trying to read in a message until ";" is received. Then send the whole message to a LCD display and to a Text to Speech module (which needs an entire string sent in one shot.)
Changing to a While loop didn't seem to help....

Thanks

4

What does it do when it receives something from the client?

5

As far as we can see, concat isn't working.
ie printString doesn't get added to here:

printString = printString + thisChar;

Is thisChar a string that can be concat'ed onto another string?
char thisChar = client.read();

6

I use character arrays with strlen, strcpy and strcat. I stay away from the String data type.

7

-concatenate incoming characters to a string until the ";" character is typed

Below is some simple delimited serial capture code that should be adaptable to your telnet session code.

//zoomkat 3-5-12 simple delimited ',' string parce 
//from serial port input (via serial monitor)
//and print result out serial port
// CR/LF could also be a delimiter

String readString;

void setup() {
  Serial.begin(9600);
  Serial.println("serial delimit test 1.0"); // so I can keep track of what is loaded
}

void loop() {

  //expect a string like wer,qwe rty,123 456,hyre kjhg,
  //or like hello world,who are you?,bye!,

  if (Serial.available())  {
    char c = Serial.read();  //gets one byte from serial buffer
    if (c == ',') {
      if (readString.length() >0) {
        Serial.println(readString); //prints string to serial port out
        //do stuff with the captured readString 
        readString=""; //clears variable for new input
      }
    }  
    else {     
      readString += c; //makes the string readString
    }
  }
}