How to get information about the juice if you do not know how much data has passed?

I am working on a Python-based GUI for interacting with a Python robot and Arduino Mega as a motor controller and a sensor controller.

Initially, I was going to use Remote Desktop to download my GUI from the robot. This turned out to be very slow due to remote desktop. I decided that the server and client would be better.

I have a sketch working on my Arduino that catches engine commands and executes them. He also expects the Ping command to pass, and at this time she must check the ultrasound transducer in three different positions, then write this information back to the server, which must catch this data and, in turn, transmit it to the GUI client. I got the most to work, but I can’t get the data from the server back to the client. I thought a simple "client.recv ()" would do this, but it is not.

How can I get this data if I don’t know exactly how much data is being returned?

Arduino sends data as "dist1, dist2, dist3 \ n".

Here is my Arduino code:

#include <LiquidCrystal.h>
#include <Ping.h>
#include <Servo.h>
// Parallax Ping Unit for distance sensing.
Ping sonic(22);

// Setup LCD pins.
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

// Servo for Ping unit sweeping.
Servo  PingServo;

// Setup Ping distance setting variables.
int pingDisCent;
int pingDisLeft;
int pingDisRight;

// Variable to keep commands in.
char MsgRcvd;

// Motor setup information.

int LF[] = {23,24};
int LR[] = {25,26};
int RF[] = {27,28};
int RR[] = {29,30};

// Set Debugging here
// 1 - Debug on - Motors don't turn when commands are sent.
// 0 - Debug off - Motors turn when commands are sent.
int debug = 1;

//Variables for speed
int SpdPin = 22;
int Speed = 255;

void setup()
{
  Serial.begin(9600);  // start serial communications

  // Setup motors for output.
  int i;
  for(i = 0; i < 2; i++){
    pinMode(LF[i], OUTPUT);
    pinMode(LR[i], OUTPUT);
    pinMode(RF[i], OUTPUT);
    pinMode(RR[i], OUTPUT);
  }

  // Setup servo to sweep.
  PingServo.attach(6);
  PingServo.write(90);

  // Set up the LCD number of rows and columns:
  lcd.begin(16, 2);

  // Print a message to the LCD.
  lcd.print("Waiting...");

  // Setup speed pin.
  pinMode(SpdPin, OUTPUT);
}

void loop()
{
  if (Serial.available() > 0)    //Check to see if a command is available.
  {
    MsgRcvd = Serial.read();    // If a command is there, see what it is.
    switch (MsgRcvd)
    {
      case '0':
        Stop();
        break;
      case '1':
        MoveForward();
        break;
      case '2':
        MoveLeft();
        break;
      case '3':
        MoveRight();
        break;
      case '4':
        MoveBackward();
        break;
      case '~':
        active_ir();
        break;
      case 'M':                    // Check to see if we have a connection from the GUI - if so spit out information to the LCD.
        lcd.clear();
        lcd.print("Connected");
        lcd.setCursor(0,1);
        lcd.print("waiting..");
        break;
      case 'D':
        lcd.setCursor(0,1);
        lcd.print("Disconnected"); // Client disconnected - spit out a disconnect to the LCD.
        break;
    }
  }
  delay(100);
}

//  ===================================
//  =====    Ping Ultrasonic      =====
//  ===================================
void active_ir()
{
  // Read to the right.
  PingServo.write(30);
  delay(300);
  pingDisRight = sonic.inch();
  delay(500);

  // Read to the front.
  PingServo.write(90);
  delay(300);
  pingDisCent = sonic.inch();
  delay(500);
  //  Read to the left.
  PingServo.write(150);
  delay(300);
  pingDisLeft = sonic.inch();
  delay(500);
  Serial.print(pingDisLeft);
  Serial.print(',');
  Serial.print(pingDisCent);
  Serial.print(',');
  Serial.println(pingDisRight);
  return;
}



//  ==========================================
//  ======        MOTOR CONTROL      =========
//  ==========================================

void MoveForward()
{
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Forward");
  if (debug == 0){

    digitalWrite(LF[0], HIGH);
    digitalWrite(LF[1], LOW);
    digitalWrite(LR[0], HIGH);
    digitalWrite(LR[1], LOW);
    digitalWrite(RF[0], HIGH);
    digitalWrite(RF[1], LOW);
    digitalWrite(RR[0], HIGH);
    digitalWrite(RR[1], LOW);
  }
}

void MoveBackward()
{
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Reverse");
  if (debug == 0){
    analogWrite(SpdPin, Speed);
    digitalWrite(LF[0], LOW);
    digitalWrite(LF[1], HIGH);
    digitalWrite(LR[0], LOW);
    digitalWrite(LR[1], HIGH);
    digitalWrite(RF[0], LOW);
    digitalWrite(RF[1], HIGH);
    digitalWrite(RR[0], LOW);
    digitalWrite(RR[1], HIGH);
  }
}

void MoveLeft()
{
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Left");
  if (debug == 0){
    analogWrite(SpdPin, Speed);
    digitalWrite(LF[0], LOW);
    digitalWrite(LF[1], HIGH);
    digitalWrite(LR[0], LOW);
    digitalWrite(LR[1], HIGH);
    digitalWrite(RF[0], HIGH);
    digitalWrite(RF[1], LOW);
    digitalWrite(RR[0], HIGH);
    digitalWrite(RR[1], LOW);
  }
}

void MoveRight()
{
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Right");
  if (debug == 0) {
    analogWrite(SpdPin, Speed);
    digitalWrite(LF[0], HIGH);
    digitalWrite(LF[1], LOW);
    digitalWrite(LR[0], HIGH);
    digitalWrite(LR[1], LOW);
    digitalWrite(RF[0], LOW);
    digitalWrite(RF[1], HIGH);
    digitalWrite(RR[0], LOW);
    digitalWrite(RR[1], HIGH);
  }
}

void Stop()
{
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Stopping");
  if (debug == 0){
    digitalWrite(LF[0], LOW);
    digitalWrite(LF[1], LOW);
    digitalWrite(LR[0], LOW);
    digitalWrite(LR[1], LOW);
    digitalWrite(RF[0], LOW);
    digitalWrite(RF[1], LOW);
    digitalWrite(RR[0], LOW);
    digitalWrite(RR[1], LOW);
  }
}

Here is my Python server code:

import serial
import socket

Serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
Serv.bind(('', 9000))
Serv.listen(1)
print "Listening on TCP 9000"
motor = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
print "Connected to Motor Controller: /dev/ttyUSB0"

while(1):
    print "Waiting For Connection..."
    connection, addr = Serv.accept()
    connection.setblocking(0)
    print "Connected by", addr[0]
    while(1):
        try:
            Servdata = connection.recv(1)
            break
        except:
            pass
    if (Servdata == 'M'):
        print "Entering Manual Mode"
        motor.write(Servdata)
        while(Servdata != 'X'):
            Servdata = '9'
            try:
                Servdata = connection.recv(1)
            except:
                pass
            if Servdata == 'X':
                print "Exiting"
                break
            if Servdata == '0':
                print "Stopping"
                motor.write(Servdata)
            if Servdata == '1':
                print "Forward"
                motor.write(Servdata)
            if Servdata == '2':
                print "Left"
                motor.write(Servdata)
            if Servdata == '3':
                print "Right"
                motor.write(Servdata)
            if Servdata == '4':
                motor.write(Servdata)
                print "Backwards"
            if Servdata == '~':
                motor.write(Servdata)
                retval = motor.readline()
                Serv.send(retval)
            else:
                pass
        motor.write('0')
        connection.close()
        print addr[0], "Closed Manual Mode"

, : GUI- ( , ...):

from socket import *
from PythonCard import model
HOST = ''
PORT = 9000
ADDR = (HOST,PORT)
BUFSIZE = 4096
Client = socket (AF_INET,SOCK_STREAM)
Client.connect((ADDR))
Client.send('M')
class MainWindow(model.Background):
    def on_SetSpdBtn_mouseClick(self, event):
        spd = self.components.SpdSpn.value
    def on_FwdBtn_mouseClick(self, event):
        spd = self.components.SpdSpn.value
        Client.send('1')
    def on_LftBtn_mouseClick(self, event):
        spd = self.components.SpdSpn.value
        Client.send('2')
    def on_RitBtn_mouseClick(self, event):
        spd = self.components.SpdSpn.value
        Client.send('3')
    def on_RevBtn_mouseClick(self, event):
        spd = self.components.SpdSpn.value
        Client.send('4')
    def on_StpBtn_mouseClick(self, event):
        spd = self.components.SpdSpn.value
        Client.send('0')
    def on_GetPing_mouseClick(self, event):
        Client.send('~')
        retval = Client.recv()
        ping_data = retval.strip() # Strip out the newline, if you read an entire line.
        split_data = ping_data.split(',')
        L_Ping = split_data[0]
        R_Ping = split_data[1]
        self.components.PingLeft.text = str(L_Ping)
        self.components.PingRight.text = str(R_Ping)
app = model.Application(MainWindow)
app.MainLoop()