Backstory: what I have done
{Codes at the bottom} I've already coded the multithreaded client and server programs using python socket, with the help of the following sites:
I. Echo Client and Server
II. Socket Server with Multiple Clients | Multithreading | Python
III. Python Socket Receive Large Amount of Data
Regarding Encryption & Decryption
(1) Exactly at what places in my codes should I encrypt/decrypt my message? Do
I encrypt the messages themselves after the user inputs or do I encrypt the byte streams after the input messages have been encoded?
(2) And how am I supposed to encrypt/decrypt the communication properly and efficiently? (It'd be nice to see code solutions with explanation, many thanks)
My Codes Currently
_server.py
import socket
import os
from _thread import *
import struct # Here to convert Python data types into byte streams (in string) and back
# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)
def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)
def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
# ---- Server Communication Setup
HOST = '127.0.0.1' # Standard loopback interface address (localhost)
PORT = 65432 # Port to listen on (non-privileged ports are > 1023)
ThreadCount = 0
try: # create socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))
try: # bind socket to an address
s.bind((HOST, PORT))
except socket.error as e:
print(str(e))
print('Waitiing for a Connection..')
s.listen(3)
def threaded_client(conn: socket):
conn.send(str.encode('Welcome to the Server'))
while True:
# data = conn.recv(2048) # receive message from client
data = recv_msg(conn)
reply = 'Server Says: ' + data.decode('utf-8')
if not data:
break
# conn.sendall(str.encode(reply))
send_msg(conn, str.encode(reply))
conn.close()
while True:
Client, addr = s.accept()
print('Connected to: ' + addr[0] + ':' + str(addr[1]))
start_new_thread(threaded_client, (Client, )) # Calling threaded_client() on a new thread
ThreadCount += 1
print('Thread Number: ' + str(ThreadCount))
s.close()
_client.py
import socket
import struct # Here to convert Python data types into byte streams (in string) and back
# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)
def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)
def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
# ---- Client Communication Setup ----
HOST = '127.0.0.1' # The server's hostname or IP address
PORT = 65432 # The port used by the server
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))
print('Waiting for connection')
try:
s.connect((HOST, PORT))
except socket.error as e:
print(str(e))
Response = s.recv(1024)
while True:
Input = input('Say Something: ')
# s.send(str.encode(Input))
send_msg(s, str.encode(Input))
# Response = s.recv(1024)
Response = recv_msg(s)
print(Response.decode('utf-8'))
s.close()
You only need to Encrypt the Message itself. I would use RSA to Encrypt the Messages.
If you plan on using multiple Servers, you can open a second Port and if someone connects to it, the Server/Host. Sends the Public Key to the Client.
After that, the Client sends his Public key to the Server.
Now Server and Client switch Ports, and Communicate over there while using the Public key of the other to Encrypt the Messages and decrypt them with their Private key.
You can also Hard-code the Public Keys, if you only have one Server and one Client.
A good Module for RSA Encryption is PyCrytodome.
Here is an Example of to encrypt messages with PyCrytodome.
from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP
def encrypt(pk_receiver, message):
key = RSA.import_key(pk_receiver)
cipher = PKCS1_OAEP.new(key)
c = cipher.encrypt(message.encode())
return c
def decrypt(sk, c):
key = RSA.import_key(sk)
cipher = PKCS1_OAEP.new(key)
m = cipher.decrypt(c)
return m
def generate_sk(key_length):
key = RSA.generate(key_length)
with open('./secret_key.pem', 'wb') as f:
f.write(key.export_key(format='PEM'))
return key
def generate_pk(sk):
pk = sk.public_key()
with open('./public_key.pem', 'wb') as f:
f.write(pk.export_key(format='PEM'))
return
Related
I am attempting to piece together a secure socket client server communication solution. I do not have experience in doing so, so have cobbled together what I believe are relevant sections. The idea is that the Server waits for connections, the client creates a connection that is secure and then communication can take place.
The code also utilizes secure communication in authorization with client and server keys and certificates.
client code:
class Client:
def __init__(self):
try:
self.host, self.port = "127.0.0.1", 65416
self.client_cert = os.path.join(os.path.dirname(__file__), "client.crt")
self.client_key = os.path.join(os.path.dirname(__file__), "client.key")
self._context = ssl.SSLContext()
self._context.load_cert_chain(self.client_cert, self.client_key)
self._sock = None
self._ssock = None
except Exception as e:
print("Error in Initializing")
def checkvalidclient(self):
# ---- Client Communication Setup ----
HOST = self.host # The server's hostname or IP address
PORT = self.port # The port used by the server
try:
self._sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self._ssock = self._context.wrap_socket(self._sock,)
self._ssock.connect((HOST, PORT))
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))
print('Waiting for connection')
Response = self._ssock.recv(1024)
while True:
Input = input('Say Something: ')
# s.send(str.encode(Input))
send_msg(self._ssock, str.encode(Input))
# Response = s.recv(1024)
Response = recv_msg(self._ssock)
if Response is not None:
print(Response.decode('utf-8'))
def closesockconnection(self):
self._ssock.close()
# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)
def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)
def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
client = Client()
client.checkvalidclient()
Server code:
import socket
import os
import ssl
from os import path
from _thread import *
import struct # Here to convert Python data types into byte streams (in string) and back
# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)
def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)
def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
try:
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
except Exception as e:
print("Exception in recvall : " + str(e))
# ---- Server Communication Setup
class Server:
def __init__(self):
self.HOST = '127.0.0.1' # Standard loopback interface address (localhost)
self.PORT = 65416 # Port to listen on (non-privileged ports are > 1023)
self.ThreadCount = 0
self.server_cert = path.join(path.dirname(__file__), "server.crt")
self.server_key = path.join(path.dirname(__file__), "server.key")
self.client_cert = path.join(path.dirname(__file__), "client.crt")
self._context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
self._context.verify_mode = ssl.CERT_REQUIRED
self._context.load_cert_chain(self.server_cert, self.server_key)
self._context.load_verify_locations(self.client_cert)
self.sock = None
def connect(self):
try: # create socket
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))
try: # bind socket to an address
self.sock.bind((self.HOST, self.PORT))
except socket.error as e:
print(str(e))
print('Waiting for a Connection..')
self.sock.listen(3)
def threaded_client(self, conn: socket):
conn.send(str.encode('Welcome to the Server'))
while True:
# data = conn.recv(2048) # receive message from client
data = recv_msg(conn)
print(data)
if data is not None:
reply = 'Server Says: ' + data.decode('utf-8')
if not data:
break
# conn.sendall(str.encode(reply))
send_msg(conn, str.encode(reply))
#conn.close()
def waitforconnection(self):
while True:
Client, addr = self.sock.accept()
self._context.wrap_socket(Client, server_side=True)
print('Connected to: ' + addr[0] + ':' + str(addr[1]))
start_new_thread(self.threaded_client, (Client, )) # Calling threaded_client() on a new thread
self.ThreadCount += 1
print('Thread Number: ' + str(self.ThreadCount))
#self.sock.close()
server = Server()
server.connect()
server.waitforconnection()
The lines:
def threaded_client(self, conn: socket):
conn.send(str.encode('Welcome to the Server'))
result in the error:
[WinError 10038] An operation was attempted on something that is not a socket
When I removed the certificate related lines in client:
self.client_cert = os.path.join(os.path.dirname(__file__), "client.crt")
self.client_key = os.path.join(os.path.dirname(__file__), "client.key")
self._context = ssl.SSLContext()
self._context.load_cert_chain(self.client_cert, self.client_key)
and the certificate related lines in the server:
self.server_cert = path.join(path.dirname(__file__), "server.crt")
self.server_key = path.join(path.dirname(__file__), "server.key")
self.client_cert = path.join(path.dirname(__file__), "client.crt")
self._context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
self._context.verify_mode = ssl.CERT_REQUIRED
self._context.load_cert_chain(self.server_cert, self.server_key)
self._context.load_verify_locations(self.client_cert)
self.sock = None
and a couple of small changes to remove the certificate related functionality, everything seemed to work, the client could send messages to the server and the server could respond (and the client displayed the response).
When however I added the context related certificates I start getting the error:
An operation was attempted on something that is not a socket
The server waits at:
Client, addr = self.sock.accept()
and continues to run once the client has called (in the client.py file):
self._ssock.connect((HOST, PORT))
The server then reaches the lines:
def threaded_client(self, conn: socket):
conn.send(str.encode('Welcome to the Server'))
where it fails on this error.
Printing the terminal, a traceback and exception error results in:
Socket successfully created
Waiting for a Connection..
Connected to: 127.0.0.1:57434
Thread Number: 1
Traceback (most recent call last):
File "c:\testcode\Server.py", line 71, in threaded_client
conn.send(str.encode('Welcome to the Server'))
OSError: [WinError 10038] An operation was attempted on something that is not a socket
My knowledge is limited and I cannot find more examples of secure multi threaded two way communication client to server socket code. The idea is to ensure the client is authorized to communicate with the server before transmission happens.
Any ideas on where I am failing?
Thanks
Ok, It seems like I was close, but had a couple of tweaks to do.
The solution of:
SSL/TLS client certificate verification with Python v3.4+ SSLContext
and the commenters here, helped me get over the finish line.
Server code:
import socket
import os
from socket import AF_INET, SOCK_STREAM, SO_REUSEADDR, SOL_SOCKET, SHUT_RDWR
import ssl
from os import path
from _thread import *
import struct # Here to convert Python data types into byte streams (in string) and back
import traceback
# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)
def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)
def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
try:
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
except Exception as e:
print("Exception in recvall : " + str(e))
# ---- Server Communication Setup
class Server:
def __init__(self):
self.HOST = '127.0.0.1' # Standard loopback interface address (localhost)
self.PORT = 65416 # Port to listen on (non-privileged ports are > 1023)
self.ThreadCount = 0
self.server_cert = path.join(path.dirname(__file__), "server.crt")
self.server_key = path.join(path.dirname(__file__), "server.key")
self.client_cert = path.join(path.dirname(__file__), "client.crt")
self._context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
self._context.verify_mode = ssl.CERT_REQUIRED
self._context.load_cert_chain(certfile=self.server_cert, keyfile=self.server_key)
self._context.load_verify_locations(cafile=self.client_cert)
self.sock = None
def connect(self):
try: # create socket
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) ###<-- socket.socket() ???
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))
try: # bind socket to an address
self.sock.bind((self.HOST, self.PORT))
except socket.error as e:
print(str(e))
print('Waiting for a Connection..')
self.sock.listen(3)
def threaded_client(self, conn: socket):
try:
conn.send(str.encode('Welcome to the Server'))
while True:
data = recv_msg(conn)
print("data")
print(data)
if data is not None:
reply = 'Server Says: ' + data.decode('utf-8')
if not data:
break
send_msg(conn, str.encode(reply))
except Exception as e:
print(traceback.format_exc())
print(str(e))
finally:
print("Closing connection")
conn.shutdown(socket.SHUT_RDWR)
conn.close()
#conn.close()
def waitforconnection(self):
while True:
Client, addr = self.sock.accept()
conn = self._context.wrap_socket(Client, server_side=True)
print('Connected to: ' + addr[0] + ':' + str(addr[1]))
print("SSL established. Peer: {}".format(conn.getpeercert()))
start_new_thread(self.threaded_client, (conn, )) # Calling threaded_client() on a new thread
self.ThreadCount += 1
print('Thread Number: ' + str(self.ThreadCount))
#self.sock.close()
server = Server()
server.connect()
server.waitforconnection()
Client code:
import socket
import struct # Here to convert Python data types into byte streams (in string) and back
import sys
import ssl
import socket
import selectors
import types
import io
import os
import time
import requests
from pathlib import Path
import mysql.connector as mysql
from loguru import logger as log
from utils.misc import read_py_config
import json
import rsa
import base64
class Client:
def __init__(self):
self.host, self.port = "127.0.0.1", 65416
self.client_cert = os.path.join(os.path.dirname(__file__), "client.crt")
self.client_key = os.path.join(os.path.dirname(__file__), "client.key")
self.server_crt = os.path.join(os.path.dirname(__file__), "server.crt")
self.sni_hostname = "example.com"
self._context = ssl.create_default_context(ssl.Purpose.SERVER_AUTH, cafile=self.server_crt)
self._context.load_cert_chain(certfile=self.client_cert, keyfile=self.client_key)
self._sock = None
self._ssock = None
def checkvalidclient(self):
# ---- Client Communication Setup ----
HOST = self.host # The server's hostname or IP address
PORT = self.port # The port used by the server
try:
self._sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self._ssock = self._context.wrap_socket(self._sock, server_side=False, server_hostname=self.sni_hostname)
self._ssock.connect((HOST, PORT))
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))
print('Waiting for connection')
Response = self._ssock.recv(1024)
if Response is not None:
print(Response.decode('utf-8'))
while True:
Input = input('Say Something: ')
send_msg(self._ssock, str.encode(Input))
Response = recv_msg(self._ssock)
if Response is not None:
print(Response.decode('utf-8'))
def closesockconnection(self):
self._ssock.close()
# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)
def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)
def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
Also ensure (as per the link) that the certificate creation is correct.
There is also another useful link at:
Exploring HTTPS With Python
Which covers HTTPS, specifically the Wireshark section allows you to monitor the traffic from client to server. After completing the above and deploying Wireshark I see that the data is encrypted. Any editing of the certificates (manually) causes the app to fail.
There still needs to be additions of try and except if the communication is halted midway etc. But hoping it will smooth the journey for others.
Thanks to the commenters, helped lead me on the way to solution.
I am developing a python socket server. The client send each message to start with a STX (\x02) and end with ETX (\x03). My code can receive message successfully but I can't implement receiving full string using STX and ETX condition. Need help in resolving this issue. Below I have sharing my code for better understanding.
import socket
import time
# Start New RnD
# Global Veriable
enq = chr(5)
ack = chr(6)
stx = chr(2)
etx = chr(3)
# Connect to the server with `telnet $HOSTNAME 5000`.
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setblocking(False)
server.bind(('0.0.0.0', 5000))
server.listen(1)
connections = []
while True:
try:
connection, address = server.accept()
connection.setblocking(False)
connections.append(connection)
except BlockingIOError:
pass
# Incoming Data Processing
for connection in connections:
try:
full_message = ''
data = ""
while True:
try:
received = connection.recv(1)
if received == enq.encode('utf-8'):
print("Received <ENQ>, Sending <ACK>")
connection.sendall(ack.encode('utf-8'))
if not received:
raise RuntimeError("unexpected end-of-message", data)
data += received.decode('utf-8')
#print("Received: {!r}".format(data))
if "\x03" in received.decode("utf-8") :
break
except BlockingIOError:
pass
print("Full Received: {!r}".format(data))
print("Data Received, Sending <ACK>")
connection.sendall(ack.encode('utf-8'))
except BlockingIOError:
continue
I'm trying to send packets using sockets, and was able to do so just fine until this morning. I'm not sure what's going on. The packets are showing up in tcpdump but the server and the client cannot connect to each other.
netcat.py
import socket
import argparse
import sys
import os
import re
import threading
def convertContent(content: str = "") -> bytes:
byteContent = []
# grab the hex from the content
for i in range(len(content)):
if content[i] == "\\" and content[i+1] == "x":
byteContent.append(f"{content[i+2]}{content[i+3]}")
# grab the non hex from the content, split it on the hex
stringContent = re.split(r"\\x.{2}", content)
byteIndex = 0
newContent = b""
# Re add the non-hex content, and the hex content
for word in stringContent:
newContent += word.encode()
if byteIndex < len(byteContent):
newContent += bytes.fromhex(byteContent[byteIndex])
byteIndex += 1
newContent = newContent.replace(b"\\n", b"\n").replace(b"\\r", b"\r")
return newContent
class Netcat():
'''
Netcat class that can be used to send/receive TCP packets
'''
BUFFER_SIZE = 1024
def __init__(self):
pass
#classmethod
def createSocket(cls):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# Address might be in a TIME_WAIT status, ignore this
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# Port might be in a TIME_WAIT status, ignore this
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
return sock
#classmethod
def send(cls, hostname: str = "127.0.0.1", srcPort: int = 0, destPort: int = 9999, content: str = "", buffer_size: int = 1024):
srcPort = int(srcPort)
destPort = int(destPort)
try:
content = convertContent(content=content)
except:
pass
sock = cls.createSocket()
# Set the source port before sending
sock.connect((hostname, destPort))
sock.sendall(content)
# shutdown might be redundant/unnecessary (tells connected host that we're done sending data)
sock.shutdown(socket.SHUT_WR)
while True:
data = sock.recv(buffer_size)
if len(data) == 0:
break
sock.close()
#classmethod
def receive(cls, port: int = 9999, buffer_size: int = 1024):
if port <= 1024 and os.geteuid() != 0:
print(f"Listening on port {port} requires superuser privileges!")
return
host = ""
sock = cls.createSocket()
sock.bind((host, port))
sock.listen(10)
conn, addr = sock.accept()
while True:
data = conn.recv(buffer_size)
if not data:
break
conn.close()
threading.Thread(target=Netcat.receive,daemon=True).start()
Netcat.send(content="test")
Note: I am sending the packets from one VM to another, rather than sending to myself, but it would be a lot to ask people to spin up a bunch of VMs to reproduce this. The hostname param in the send method should be the actual IP of the receiving machine
I've thrown some print statements, and the server stops on sock.accept(), while the client hangs on sock.connect((hostname, destPort))
I checked the hostname for the server, and it's listening on (0.0.0.0, 8888) (assuming 8888 is the port param), which means its listening on all interfaces on that port, so I dont know why its refusing to connect
I tcpdumped on the server, and its getting the packets, it gets a SYN, then sends out a SYN, ACK, but the rest of the packets are marked as re-transmissions.
I've tried looping the accept & connect lines, thinking maybe some sort of race condition was occurring, but no matter what I do the client can't connect to the server.
Edit: This works on my local machine, but still breaks when I try to send packets over the network. The first 2 steps of the handshake go through SYN & SYN, ACK, but not the third ACK
Don't bind in the client. Working example below, but minor changes to make a standalone script:
import socket
import threading
def receive(port: int = 9999, buffer_size: int = 1024):
host = ""
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# Address might be in a TIME_WAIT status, ignore this
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((host, port))
sock.listen()
conn, addr = sock.accept()
while True:
data = conn.recv(buffer_size)
if not data:
break
print(data)
conn.close()
def send(hostname: str = "127.0.0.1", destPort: int = 9999, content: str = b"test", buffer_size: int = 1024):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# Address might be in a TIME_WAIT status, ignore this
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# Removed bind
sock.connect((hostname, destPort))
sock.sendall(content)
# shutdown might be redundant/unnecessary (tells connected host that we're done sending data)
sock.shutdown(socket.SHUT_WR)
while True:
data = sock.recv(buffer_size)
if len(data) == 0:
break
sock.close()
threading.Thread(target=receive,daemon=True).start()
send()
Output:
b'test'
I am trying to create a function to send and receive information over a socket client & server. It appears that my code is somehow blocking. In the code the first command iteration in my for loop is carried out but then the process becomes blocked. Does anyone have any suggestions how to do this using threading or multithreading?
My code is below:
import socket
import json
import sys
import time
import select
import queue
Ni_Rio_IP= "172.22.11.2"
Ni_Base_IP= "172.22.11.1"
class AliceRio:
def __init__(self, ip_rio, ip_pc):
self.ip_rio = ip_rio
AliceRio.udp_port_rio = 60006
self.ip_pc = ip_pc
AliceRio.udp_port_pc = 50005
AliceRio.json= '{"Dest":"","Name":"","Time":"","Val":{"Str":[],"Pos":[[]],"Data":[[]]},"IP":0,"Port":0,"RT error":{"status":false,"code":0,"source":""}}'
AliceRio.dict= json.loads(self.json)
def PrintUDP(self):
print("RIO IP: %s" % self.ip_rio)
print("RIO UDP port: %s" % self.udp_port_rio)
print("PC IP: %s" % self.ip_pc)
print("PC UDP port: %s" % self.udp_port_pc)
def SendRec(self, send_str):
# Set up socket for sending
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # Internet, UDP
sock.sendto(bytes(send_str, 'utf-8'), (self.ip_rio, self.udp_port_rio))
sock.close()
print('got here')
# Set up socket for receiving
sock = socket.socket(socket.AF_INET,socket.SOCK_DGRAM) # Internet, UDP
sock.bind((self.ip_pc, self.udp_port_pc))
rec_str, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print('got here2')
sock.close()
return rec_str
def Receive(self, rec_str):
sock = socket.socket(socket.AF_INET,socket.SOCK_DGRAM) # Internet, UDP
sock.bind((self.ip_pc, self.udp_port_pc))
rec_str, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
sock.close()
return rec_str
def Send(self, send_str):
# Set up socket for sending
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # Internet, UDP
sock.sendto(bytes(send_str, 'utf-8'), (self.ip_rio, self.udp_port_rio))
sock.close()
#return rec_str
def Aim(self, aim_perc):
if aim_perc < 0 or aim_perc > 100: return "aim_perc out of range"
send_dict=AliceRio.dict
send_dict["Dest"]='Rio'
send_dict["Name"]='Laser Control'
Laser_Mode=1
Simmer_A=0
Pulse_A= 0
Pulse_ms= 20
send_dict["Val"]["Str"]=[str(Laser_Mode), str(aim_perc), str(Simmer_A), str(Pulse_A), str(Pulse_ms)]
send_json=json.dumps(send_dict)
# send it out
self.SendRec(send_json)
rec_json= self.SendRec(send_json)
rec_dict=json.loads(rec_json)
return "Aim laser now at " + rec_dict["Val"]["Str"][1] +'%'
def PWM_Laser_Fan(self, fan_perc):
send_dict=AliceRio.dict
send_dict["Dest"]='Rio'
send_dict["Name"]='PWM Laser'
send_dict["Val"]["Str"][0]=str(fan_perc)
send_json=json.dumps(send_dict)
# send it out
rec_json= self.SendRec(send_json)
rec_dict=json.loads(rec_json)
return rec_dict["Val"]["Str"][0]
def Poll(self):
send_dict=AliceRio.dict
send_dict["Dest"]='Rio'
send_dict["Name"]='Poll'
send_json=json.dumps(send_dict)
# send it out
rec_json= self.SendRec(send_json)
rec_dict=json.loads(rec_json)
if rec_dict["Val"]["Data"][0][0]==0: pid_mode='off'
else: pid_mode='PID'
print('PID mode:', pid_mode)
print('Pos X:', rec_dict["Val"]["Data"][0][1])
print('Pos Y:', rec_dict["Val"]["Data"][0][2])
print('Home:', rec_dict["Val"]["Data"][0][3])
print('Enabled:', rec_dict["Val"]["Data"][0][4])
def PIDControl(self, pid_mode,pid_center):
if pid_mode=="off": mode= 0
elif pid_mode=="PID":mode =1
else: return "pid_mode not valid"
if pid_center[0] not in range(-2048,2048): return "center x-pos not in range"
if pid_center[1] not in range(-2048,2048): return "center y-pos not in range"
send_dict=AliceRio.dict
send_dict["Dest"]='Rio'
send_dict["Name"]='PID Control'
send_dict["Val"]["Str"]=[str(mode), str(pid_center[0]), str(pid_center[1])]
send_json=json.dumps(send_dict)
# send it out
rec_json= self.SendRec(send_json)
rec_dict=json.loads(rec_json)
return "PID mode now at " + rec_dict["Val"]["Str"][0]
Alice1 = AliceRio(Ni_Rio_IP, Ni_Base_IP)
Alice1.PrintUDP()
for i in range(10):
Alice1.Aim((i*10)+10)
time.sleep(0.2)
I would suggest learning to use Pdb and trace through the execution of your program to find where it is getting caught.
Also when learning/developing with sockets I've found that it helps to have separate programs for your client and server in the beginning so you can see how both sides are handling exchanges instead of going the threading route to start since the logging can get confusing, best of luck!
Module threading does help in this scenario.
We can create a thread to receiving incoming messages. And when new message received the thread trigger an event to notify the waiting method SendRec.
import sys
import socket
import json
import threading
import time
class AliceRio:
def __init__(self, .....):
# .........
self.s_in = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
self.s_in.bind((self.ip_pc, self.udp_port_pc))
self.evt = threading.Event()
self.last_msg = None
def _recv(self):
while True:
msg, _ = self.s_in.recvfrom(1024)
self.last_msg = msg
self.evt.set()
def SendRec(self, send_str):
if not hasattr(self, 'th_recv'):
th = threading.Thread(target=self._recv)
th.setDaemon(True)
th.start()
self.th_recv = th
self.evt.clear()
rio_endpoint = (self.ip_rio, self.udp_port_rio)
s_out = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s_out.sendto(bytes(send_str, 'utf-8'), rio_endpoint)
s_out.close()
if self.evt.wait(timeout=15.0) and self.last_msg:
return self.last_msg
raise Exception('timeout waiting for response.')
I'm trying to send a 2D array across a socket, it needs to be made out of multiple socket.recv() otherwise I will get a _pickle.UnpicklingError: pickle data was truncated error.
I've tried to do this with a while loop that receives packets and appends them to a list until all data is received:
def receive(self):
packets = []
while True:
packet = self.socket.recv(1024)
if not packet:
break
packets.append(packet)
data = b"".join(packets)
data = pickle.loads(data)
return data
Just doing:
def receive(self):
data = self.socket.recv(1024)
data = pickle.loads(data)
return data
Works if I send something smaller than the 2D array e.g. a coordinate pair tuple (2, 3). But not with the 2D array.
I get a OSError: [WinError 10022] when attempting the while loop approach.
I have seen that a OSError: [WinError 10022] could be an issue with not binding the socket but I think I have done that.
I can't figure out where connections are closing and am very confused.
Rest of the code:
Server:
import socket
from _thread import start_new_thread
clients = []
def threaded(client):
while True:
data = client.recv(1024)
if not data:
print('Not Data.')
break
# Send the data received from one client to all the other clients.
for c in clients:
if c != client:
c.send(data)
client.close()
def Main():
host = ""
port = 5555
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((host, port))
print("Socket binded to port:", port)
s.listen(2)
print("Socket is listening.")
while True:
c, addr = s.accept()
clients.append(c)
print(f"Connected to: {addr[0]}:{addr[1]}")
start_new_thread(threaded, (c,))
s.close()
Client:
import socket
import pickle
class Client:
def __init__(self):
self.host = 'localhost'
self.port = 5555
self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.socket.connect((self.host, self.port))
def send(self, data):
message = pickle.dumps(data)
try:
self.socket.send(message)
except socket.error as e:
return str(e)
def receive(self):
packets = []
while True:
packet = self.socket.recv(1024)
if not packet:
break
packets.append(packet)
data = b"".join(packets)
data = pickle.loads(data)
return data
The client-server I want to make will have 2 clients and each client will send data to the other constantly. How can I correct my code and properly implement this?
After doing more research and figuring out what was going wrong I got a solution.
The code never got out of this while loop - because data was constantly being sent and some packet was always incoming.
def receive(self):
packets = []
while True:
packet = self.socket.recv(1024)
if not packet:
break
packets.append(packet)
A solution I found was to send a message indicating how big the message being received should be, so I can tell when all the bytes for a particular message have arrived. Links: Sockets Python 3.5: Socket server hangs forever on file receive, Python Socket Receive Large Amount of Data
def send(self, data):
message = pickle.dumps(data)
msg_len = len(message)
try:
# Send what the total length of the message to be sent is in bytes.
self.socket.send(msg_len.to_bytes(4, 'big'))
self.socket.sendall(message)
except socket.error as e:
return str(e)
def receive(self):
remaining = int.from_bytes(self.socket.recv(4), 'big')
chunks = []
while remaining:
# until there are bytes left...
# fetch remaining bytes or 4096 (whatever smaller)
chunk = self.socket.recv(min(remaining, 4096))
remaining -= len(chunk)
# write to file
chunks.append(chunk)
chunks = b"".join(chunks)
data = pickle.loads(chunks)
return data