Develop Reference

How to send data via bluetooth to Pi pico

I need a way to send data to and from my pi pico via bluetooth.
Here is the program I'm running on my pc.
Note: Everything on the pi is working correctly (tested with a bt serial terminal)
import bluetooth as bt
print("Scanning Bluetooth Devices....")
devices = bt.discover_devices(lookup_names=True)
for addr, name in devices:
print("%s : %s" % (name, addr))
dev_name = input("Enter device name: ")
dev = ""
check = False
for addr, name in devices:
if dev_name == name:
dev = addr
check = True
if not check:
print("Device Name Invalid!")
else:
print("Attempting to connect to %s : %s" % (dev_name, dev))
hostMACAddress = dev
port = 3
backlog = 1
size = 1024
s = bt.BluetoothSocket(bt.RFCOMM)
s.bind((hostMACAddress, port))
s.listen(backlog)
try:
client, clientInfo = s.accept()
while 1:
data = client.recv(size)
if data:
print(data)
client.send(data) # Echo back to client
except:
print("Closing socket")
client.close()
s.close()
It doesn't throw any errors but I don't get anything printed to the terminal when the pi should send "R"
Edit: Here is the working code for anyone interested :)
import bluetooth as bt
print("Scanning Bluetooth Devices....")
devices = bt.discover_devices(lookup_names=True)
for addr, name in devices:
print("%s : %s" % (name, addr))
dev_name = input("Enter device name: ")
dev = ""
check = False
for addr, name in devices:
if dev_name == name:
dev = addr
check = True
if not check:
print("Device Name Invalid!")
else:
print("Sending data to %s : %s" % (dev_name, dev))
hostMACAddress = dev
port = 1
backlog = 1
size = 8
s = bt.BluetoothSocket(bt.RFCOMM)
try:
s.connect((hostMACAddress, port))
except:
print("Couldn't Connect!")
s.send("T")
s.send("E")
s.send("S")
s.send("T")
s.send(".")
s.close()

The most straight forward (but not the most efficient way) is to convert the array of integer to a delimited C string and send it the way you are sending "Ready".
Let assume the array delimiters are "[" and "]" then the following array
int arr[] = {1,2,3};
can be converted to a string like the following
char str[] = "[010203]";
To convert array of integer to the delimited string you can do the following:
int arr[] = {1,2,3};
int str_length = 50; // Change the length of str based on your need.
char str[str_length] = {0};
int char_written = 0;
char_written = sprintf(str,'[');
for (int i = 0; i< sizeof(arr)/sizeof(int) - 1; i++){
char_written = sprintf(&str[char_written], "%02d", arr[i]);
char_written = sprintf(&str[char_written], ']');
Now you can use your existing code to send this string. In the receiving end, you need to process the string based on "[", "]", and the fact that each integer has width of 2 in the string.
Edit: Converting array to string and send the string via bluetooth via python.
To convert an array to string in python the following will do the job
a = [1,2,3,4,5]
a_string = "[" + "".join(f"{i:02d}" for i in a) + "]"
To send this string via python over bluetooth you need to use PyBlues library.
First you need to find the MAC address of the pico bluetooth
import bluetooth
# Make sure the only bluetooth device around is the pico.
devices = bluetooth.discover_devices()
print(devices)
Now that you know the MAC address, you need to connect to it
bt_mac = "x:x:x:x:x:x" # Replace with yours.
port = 1
sock=bluetooth.BluetoothSocket(bluetooth.RFCOMM)
sock.connect((bd_addr, port))
Know you can send strings like
sock.send(a_string.encode())
Finally, in the end of your python program close the socket
sock.close()
PS: I do not have bluetooth available to test it but it should work.

How to send a base64 encoded image via tcp from python to node js?

I am basically working on a project and got stuck at this point. I tried normal tcp but later found that the image was partially transported of max length around 65,000 at node js end. But the total encoded image length is around 3 times of 65000 at python side. The image is basically a screen-shot of my desktop of resolution around 1920 x 1020.
Here is my python side code
import socket
HOST = '127.0.0.1' # Standard loopback interface address (localhost)
PORT = 9898 # Port to listen on (non-privileged ports are > 1023)
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen()
print("-- start --")
conn, addr = s.accept()
print("-- accepted --")
with conn:
print('Connected by', addr)
while True:
data = conn.recv(1024)
print("R : ", data)
if not data:
break
print("sending data")
# b64str is a pre computed string of length around 65000*3
conn.sendall(bytes(b64str, 'utf-8'))
Here is Node js side code
client.connect(9898, '127.0.0.1', function() {
console.log('CONNECTED : img-data-channel');
});
// buff is a buffer queue that stores the base64 encoded string
client.on('data', function(data) {
str_data = String.fromCharCode.apply(null, data);
buff.push_data(str_data);
// console.log("Received: img-data type : ", typeof(str_data), " size : ", str_data.length) ;
});
client.on('close', function() {
console.log('DISCONNECTED : img-data-channel');
});
Thankyou in advance.

Python how to use string in multiple scripts

I'm running a python script on a raspberry pi that reads keyboard input to a string and will be sending that string through TCP. I've made two script one that reads the input and one that can send the string if needed. How can i use one string and use it in both scripts for readings and writings?
I've used an text document. Only becaue of the sd card i wanne achieve an connecting between the two scripts
Reading part:
#loops for Barcode_Data
def Create_File():
file = open("Barcode_data.txt", "w")
file.write(" // ")
file.close()
empty = ''
def Barcode_Read():
Barcode_Data= input("Input: ",)
print(Barcode_Data)
file = open("Barcode_data.txt", "a")
file.write(Barcode_Data)
file.write(" // ")
file.close()
#Loop that will only run once
Create_File()
#Loop that will run continuesly
while True:
Barcode_Read()
TCP Server:
#TCP server
def TCP_Connect(socket):
socket.listen()
conn, addr = socket.accept()
with conn:
data = conn.recv(1024)
if data == b'Barcode_Data':
tcp_file = open("Barcode_data.txt", "r")
Barcode_Data = tcp_file.read()
tcp_file.close()
conn.sendall(Barcode_Data.encode('utf-8'))
elif data == b'Clear Barcode_Data':
tcp_file = open("Barcode_data.txt", "w")
tcp_file.write(" // ")
tcp_file.close()
#TCP Socket setup
HOST = '' # Standard loopback interface address (localhost)
PORT = 1025 # Port to listen on (non-privileged ports are > 1023)
import socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
#Loop that wil run continuesly
while True:
TCP_Connect(s)

You can use the code from this question as is: Interprocess communication in Python
Server process:
from multiprocessing.connection import Listener
address = ('localhost', 6000) # family is deduced to be 'AF_INET'
listener = Listener(address, authkey='secret password')
conn = listener.accept()
print 'connection accepted from', listener.last_accepted
while True:
msg = conn.recv()
# do something with msg
if msg == 'close':
conn.close()
break
listener.close()
Client process:
from multiprocessing.connection import Client
address = ('localhost', 6000)
conn = Client(address, authkey='secret password')
conn.send('close')
# can also send arbitrary objects:
# conn.send(['a', 2.5, None, int, sum])
conn.close()
Documentation is available here: https://docs.python.org/3.7/library/multiprocessing.html#multiprocessing-listeners-clients

Socket Programming; File corrupts when transferring over multiple devices

The problem I'm having is to get a file from the server to client across devices. Everything works fine on localhost.
Lets say I want to "get ./testing.pdf" which sends the pdf from the server to the client. It sends but it is always missing bytes. Is there any problems with how I am sending the data. If so how can I fix it? I left out the code for my other functionalities since they are not used for this function.
sending a txt file with "hello" in it works perfectly
server.py
import socket, os, subprocess # Import socket module
s = socket.socket() # Create a socket object
host = socket.gethostname() # Get local machine name
#host = ''
port = 5000 # Reserve a port for your service.
bufsize = 4096
s.bind((host, port)) # Bind to the port
s.listen(5) # Now wait for client connection.
while True:
c, addr = s.accept() # Establish connection with client.
print 'Got connection from', addr
while True:
userInput = c.recv(1024)
.... CODE ABOUT OTHER FUNCTIONALITY
elif userInput.split(" ")[0] == "get":
print "inputed get"
somefile = userInput.split(" ")[1]
size = os.stat(somefile).st_size
print size
c.send(str(size))
bytes = open(somefile).read()
c.send(bytes)
print c.recv(1024)
c.close()
client.py
import socket, os # Import socket module
s = socket.socket() # Create a socket object
host = socket.gethostname() # Get local machine name
#host = '192.168.0.18'
port = 5000 # Reserve a port for your service.
bufsize = 1
s.connect((host, port))
print s.recv(1024)
print "Welcome to the server :)"
while 1 < 2:
userInput = raw_input()
.... CODE ABOUT OTHER FUNCTIONALITY
elif userInput.split(" ")[0] == "get":
print "inputed get"
s.send(userInput)
fName = os.path.basename(userInput.split(" ")[1])
myfile = open(fName, 'w')
size = s.recv(1024)
size = int(size)
data = ""
while True:
data += s.recv(bufsize)
size -= bufsize
if size < 0: break
print 'writing file .... %d' % size
myfile = open('Testing.pdf', 'w')
myfile.write(data)
myfile.close()
s.send('success')
s.close

I can see two problems right away. I don't know if these are the problems you are having, but they are problems. Both of them relate to the fact that TCP is a byte stream, not a packet stream. That is, recv calls do not necessarily match one-for-one with the send calls.
size = s.recv(1024) It is possible that this recv could return only some of the size digits. It is also possible that this recv could return all of the size digits plus some of the data. I'll leave it for you to fix this case.
data += s.recv(bufsize) / size -= bufsize There is no guarantee that that the recv call returns bufsize bytes. It may return a buffer much smaller than bufsize. The fix for this case is simple: datum = s.recv(bufsize) / size -= len(datum) / data += datum.

python tcp server sending data to multiple clients

i am having trouble trying to send data to all clients connected on my python tcp chat server. i know how to get the message/data to send right back to the person who sent it but it just won't send back if i have multiple clients. this is my server so far:
host = '127.0.0.1'
port = 4446
backlog = 5
size = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind( (host, port) )
s.listen(backlog)
clients = [s]
while 1:
inputReady, outputReady, exceptReady = select.select(clients, [], [])
for x in inputReady:
if x == s:
csock, addr = s.accept()
clients.append(csock)
else:
data = x.recv(size)
if data:
for i in clients: #problem i believe is in here but i
i.send(data) #dont know how to fix it
else:
x.close()
clients.remove(x)
s.close()
i am using node.js for the client side and its very simple so far and i dont think its the problem:
var net = require('net');
var readline = require('readline');
var host = process.argv[2];
var port = process.argv[3];
var username = process.argv[4];
var client = new net.Socket();
client.connect(port, host, function(){
var type = "connect";
var sender = username;
var msg = "has connected";
var s = type + ':' + sender + ':' + msg;
var length = s.length;
client.write(length + " " + s);
});
client.on('data', function(data){
console.log(data.toString('UTF-8'));
});

The problem is that you are sending on all sockets, including the server socket (s). Ignoring other potential problems, you can do a quick fix by doing this:
for i in clients:
if i is not s:
i.send(data)