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Error in Python code in controlling servo motor using Raspberry Pi 3 B+

I am currently building an automated trash bin using Raspberry Pi 3 B+ with Android application support where I would use a servo motor as an actuator for the lid and the Android application as a form of wireless remote control. Everything went on smoothly until I've encountered a problem that whenever I attempt to press a button on my Android application, the Python shell program has errors during testing. I've used a reference video (https://www.youtube.com/watch?v=t8THp3mhbdA&t=1s) and followed everything thoroughly until I've hit this roadblock.
The results to me that keeps appearing are:
Waiting for connection
...connected from :
Where the supposed result, according to the reference video, is:
Waiting for connection
...connected from : ('192.168.1.70', 11937)
Increase: 2.5
As you can see, the IP address, the port, and 'Increase' text doesn't appear, meaning there is something wrong with the code.
According to some comments that was made by the people who watched the video, this code is outdated, using Python 2, and the latest version we have now is Python 3, and that we need to use a ".encode()" line in a condition. However, as someone who is still new to Python, I'm afraid that I still don't have the knowledge to apply this on the code.
Here is the code that was used in the video:
import Servomotor
from socket import *
from time import ctime
import RPi.GPIO as GPIO
Servomotor.setup()
ctrCmd = ['Up','Down']
HOST = ''
PORT = 21567
BUFSIZE = 1024
ADDR = (HOST,PORT)
tcpSerSock = socket(AF_INET, SOCK_STREAM)
tcpSerSock.bind(ADDR)
tcpSerSock.listen(5)
while True:
print 'Waiting for connection'
tcpCliSock,addr = tcpSerSock.accept()
print '...connected from :', addr
try:
while True:
data = ''
data = tcpCliSock.recv(BUFSIZE)
if not data:
break
if data == ctrCmd[0]:
Servomotor.ServoUp()
print 'Increase: ',Servomotor.cur_X
if data == ctrCmd[1]:
Servomotor.ServoDown()
print 'Decrease: ',Servomotor.cur_X
except KeyboardInterrupt:
Servomotor.close()
GPIO.cleanup()
tcpSerSock.close();
I have already changed the text strings that used the ' ' format into the (" ") format since it also produced some errors in the code which I corrected immediately.
Any help will be greatly appreciated and thank you in advance!

Here's a Python3 version, edited a tiny bit for better clarity and good practice:
import Servomotor
import RPi.GPIO as GPIO
import socket
# Setup the motor
Servomotor.setup()
# Declare the host address constant - this will be used to connect to Raspberry Pi
# First values is IP - here localhost, second value is the port
HOST_ADDRESS = ('0.0.0.0', 21567)
# Declare the buffer constant to control receiving the data
BUFFER_SIZE = 4096
# Declare possible commands
commands = 'Up', 'Down'
# Create a socket (pair of IP and port) object and bind it to the Raspberry Pi address
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind(HOST_ADDRESS)
# Set the socket to listen to an incoming connection (1 at a time)
server_socket.listen(1)
# Never stop the server once it's running
while True:
# Inform that the server is waiting for a connection
print("Waiting for connection to the following address: {}...".format(HOST_ADDRESS))
# Perform a blocking accept operation to wait for a client connection
client_socket, client_address = server_socket.accept()
# Inform that the client is connected
print("Client with an address {} connected".format(client_address))
# Keep exchanging data
while True:
try:
# Receive the data (blocking receive)
data = client_socket.recv(BUFFER_SIZE)
# If 0-byte was received, close the connection
if not data:
break
# Attempt to decode the data received (decode bytes into utf-8 formatted string)
try:
data = data.decode("utf-8").strip()
except UnicodeDecodeError:
# Ignore data that is not unicode-encoded
data = None
# At this stage data is correctly received and formatted, so check if a command was received
if data == commands[0]:
Servomotor.ServoUp()
print("Increase: {}".format(Servomotor.cur_X))
elif data == commands[1]:
Servomotor.ServoDown()
print("Decrease: {}".format(Servomotor.cur_X))
elif data:
print("Received invalid data: {}".format(data))
# Handle possible errors
except ConnectionResetError:
break
except ConnectionAbortedError:
break
except KeyboardInterrupt:
break
# Cleanup
Servomotor.close()
GPIO.cleanup()
client_socket.close()
# Inform that the connection is closed
print("Client with an address {} disconnected.".format(client_address))
To show you the code in action, I have hosted a local server on my machine and connected to it using Putty. Here are the commands I have entered:
Here is the output of the server (I have swapped the Servo-related functions to print statements):
Waiting for connection to the following address: ('0.0.0.0', 21567)...
Client with an address ('127.0.0.1', 61563) connected.
Received invalid data: Hello
Received invalid data: Let's try a command next
Running ServoUp
Increase: 2.5
Running ServoDown
Decrease: 2.5
Received invalid data: Nice!
Client with an address ('127.0.0.1', 61563) disconnected.
Waiting for connection to the following address: ('0.0.0.0', 21567)...

Problems with sockets

I'm trying to set up a small server where when the client logs in gets some messages.
The server code
import socket
#Networking
s = socket.socket()
print("Network successfully created")
port = 3642
s.bind(('',port))
print("Network has been binded to %s" %(port))
s.listen(5)
print("Waiting for connections")
while True:
c, addr = s.accept()
print("Got a connection from",addr)
c.send(bytes("Thank you for connecting to me. Currently we","utf-8"))
c.send(bytes("Working on the server","utf-8"))
c.close()
This is the client code
# Import socket module
import socket
# Create a socket object
s = socket.socket()
# Define the port on which you want to connect
port = 3642
# connect to the server on local computer
s.connect(('MyIp..', port))
# receive data from the server
print(s.recv(1024))
# close the connection
s.close()
Everything works fine such as the connecting and the first message gets printed, however I can't get the second message to get printed. The one that says working on the server. I have just began learning about sockets and barely know anything about them so the solution probably is obvious it's just
I can't seem to figure it out. Thank you for any responses. (I would appreciate thorough responses)

If the two sent buffers happen to not get consolidated into a single buffer in the recv (which can happen based on timing, which OS you're running and other factors), then it makes sense that you would not see the second buffer because you're only making one recv call. If you want to receive everything the server sent, put the recv in a loop until it returns an empty string. (Empty string indicates end-of-file [i.e. socket closed by the other end].) – Gil Hamilton

Accepting multiple clients in python socket server

I'm trying to build a simple socket server in python:
import socket
import threading
import time
def handle(conn_addr):
print("Someone Connected")
time.sleep(4)
print("And now I die")
host = ''
port = 5000
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
s.bind((host,port))
except socket.error as e:
print(str(e))
s.listen(2)
while True:
threading.Thread(handle(s.accept())).start()
print("Should never be reached")
The socket server should accept multiple clients at the same time. I tried to test its functionality by calling telnet localhost 5000 from multiple tabs from my shell however the pattern that i get is
Someone Connected
And now I die
Someone Connected
And now I die
Instead of
Someone Connected
Someone Connected
Someone Connected
I call the telnet command within 4 seconds of each other so it should have 2 messages of connected in a row however the message is only returned after the previous socket is disconnected. Why is that and how could I go round fixing this?

Its a classic mistake. You called handle() (which slept for 4 seconds) and then tried to create a thread from its result. The target should be a function reference and args should be passed separately.
threading.Thread(target=handle, args=(s.accept(),)).start()
In this version, the main thread waits for an accept and then creates the thread that runs handle.

Python: Notification System?

I am working on a chat server that runs on my local network using socket, and then I have a client program running on all of the computers in my house, and this program allows all of the clients to talk to each other.
The problem is, you have to manually update the chat log by pressing enter.
The way I want it to work, maybe, is to check for a new message every few seconds, and if there is a new one, play a sound. Does anyone know how I can do this, I'll try to figure it out on my own, as I have done with most of this project, but any help is appreciated.
Here is the server:
import socket
import sys
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = ('192.168.1.80', 10000)
print >>sys.stderr, 'starting up on %s port %s' % server_address
sock.bind(server_address)
sock.listen(1)
print 'Waiting for user...'
convo='Welcome!'
while True:
# Find connections
connection, client_address = sock.accept()
try:
data = connection.recv(999)
if data=='EMPTY':
pass
else:
print data
convo=convo+'\n'+data
connection.sendall(convo)
except:
connection.close()
Here is the client:
import socket
import sys,os
name=raw_input("Enter name: ")
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = ('192.168.1.80', 10000)
print >>sys.stderr, 'connecting to %s port %s' % server_address
while True:
message=raw_input('Message: ')
try:
os.system('cls')
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(server_address)
if message is not '':
sock.sendall(name+": "+message)
else:
sock.sendall('EMPTY')
if message=='quit':
break
x=sock.recv(999)
print x
except:
break
sock.close()
Thanks!

If you need two operations to happen at the same time (the client script needs to read input from the user and read new messages from the server), then you'd need to either use threads (one thread for reading user input, and one for reading messages from the server), or futures (since python3.2).

Here's question for playing audio in python: Play audio with Python
As for your client, why are you reconnecting to your server every single time? Anyway, if I understand the problem correctly you're blocking on user input, but also want to handle messages from the server.
Without getting complicated with threads, I would recommended using a recurring signal, which I believe could handle this. There's a function call setitimer(), which will break what you're doing and call a function every so often then return to where you were (user input). In your timer function, check for server messages, print any received, play your sound and return to user input. There's an setitimer() example enter link description here.
Might be a little ugly with the user typing, so you may need to reprint what they're currently typing, but haven't sent out (using something other than raw_input()).
For a slightly more complicated option, which may help you there's a function call select(), which can block while listening for socket input AND user input. Then you just distinguish which is which and keep it all in one loop.
while True:
# select on server socket and user input (blocks for either one)
# if here, either a message has been received or the user typed something
# if a message from server
...
playSound()
# else
# send to server

Test a pair of network sockets at the same time

I have an app X that can run on either of two computers, but on no more than one at once. I have another app Y, written in Python, that given the two possible ip addresses needs to find out which computer is running app X (if any). I've partially solved this by having a UDP service that listens on a port and responds with a 'Hello' whenever it receives some data. The client can try and send data to the app X port on each address and if it gets a response, I know the application is running on that computer.
My code so far looks like this:
def ipaddress(self):
"""Test which side responds on the status port."""
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
try:
s.settimeout(5)
s.sendto("status", (ADDR_A, PORT))
s.recvfrom(1024)
except socket.timeout:
try:
s.sendto("status", (ADDR_B, PORT))
s.recvfrom(1024)
except:
pass
else:
return ADDR_B
else:
return ADDR_A
finally:
s.close()
return None
The problem with this function is that it's called periodically whenever I want to talk to the computer running app X. It will always test ADDR_A first, and if it's not running app X then I have to wait for the socket to timeout before trying ADDR_B. Although it doesn't happen often app X could have switched computers whenever I come around trying again.
Is there a better way? I'm wondering if it's possible to connect to both computers in parallel and return as soon as one responds? Or should I cache which ip address responded first last time the function was called? How would I code these or other ideas?
Thanks.
EDIT: Here is my revised code using select:
def ipaddress(addr_a, addr_b, timeout=5):
"""Test which side responds on the status port."""
# Create UDP sockets for each address
socks = [ socket.socket(socket.AF_INET, socket.SOCK_DGRAM),
socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
]
# Send some data to each socket
for sock, addr in zip(socks, (addr_a, addr_b)):
sock.connect(addr) # do explicit connect so getpeername works
sock.send("status")
# Wait for the first to respond if any
while socks:
waiting = select.select(socks, [], socks, timeout)[0]
if waiting:
for sock in waiting:
try:
data = sock.recv(1024)
if data:
return sock.getpeername()[0]
except Exception, e:
# Occasionally get [Errno 10054] which means socket isn't really
# available, so see if other responds instead...
socks.remove(sock)
else:
break # timeout occurred
return None

You should look at select.select() which provides exactly the capability you are looking for to look at the two computers in parallel.