Эхо сервер на python

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simple echo server in python

MarcCharbo/echo-server

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README.md

Your task is to build a simple «echo» server.

• The server should automatically return to any client that connects exactly what it receives (it should echo all messages).
• You will also write a python script that, when run, will send a message to the server and receive the reply, printing it to stdout.
• Finally, you’ll do all of the above in such a way that it can be tested.

• Complete the code in echo_server.py to create a server that sends back whatever messages it receives from a client
• Complete the code in echo_client.py to create a client function that can send a message and receive a reply.
• Ensure that the tests in tests.py pass.

• Open one terminal while in this folder and execute this command: $ python echo_server.py
• Open a second terminal in this same folder and execute this command: $ python echo_client.py «This is a test message.»

Once all tasks are completed, the server should print out a message indicating the message that it received from the client, and the client should print out a message indicating that it received the message back from the server.

• Open one terminal while in this folder and execute this command: $ python echo_server.py
• Open a second terminal in this same folder and execute this command: $ python tests.py

Look at demo_client.py and demo_server.py . These demonstrate basic client/server communication as shown in class. You can play the short video demo_client_server_behavior.mp4 to see an example how these two files can be called to work together.

To complete the assignment in echo_server.py and echo_client.py , you’ll be using MOST of the same lines of code. The main difference is that the echo_server :

1. Has an outer loop that accepts a connection from a client, processes a message from that client, closes the client connection, and then repeats.
2. Has an inner loop that pulls bytes off the client connection 16 bytes at a time.
3. Also, you’re putting all of this code lives inside of a function named server .

One more hint: how do you know when you’re done pulling 16 byte chunks off of the client connection? You’re done with recv returns fewer than 16 bytes.

• Write a python function that lists the services provided by a given range of ports.
  • accept the lower and upper bounds as arguments
  • provide sensible defaults
  • Ensure that it only accepts valid port numbers (0-65535)
  • The echo server as outlined will only process a connection from one client at a time. If a second client were to attempt a connection, it would have to wait until the first message was fully echoed before it could be dealt with.
  • Python provides a module called select that allows waiting for I/O events in order to control flow. The select.select method can be used to allow our echo server to handle more than one incoming connection in «parallel».
  • Read the documentation about the select module (http://docs.python.org/3/library/select.html) and attempt to write a second version of the echo server that can handle multiple client connections in «parallel». You do not need to invoke threading of any kind to do this.

  About

  simple echo server in python

  Источник

  Echo server using python and sockets

  This post explains how to create a create a simple echo server using python and sockets.
  In the first example we will create a simple echo server allowing one connection and a simple echo client, in the second example we will improve the first example allowing multiple client to be connected.

  Version used in this tutorial:

  NOTE: In all scripts is present the hash bang for MacOS, you don’t need it if you call the script using the python interpreter, i.e.: python my_test_server.py
  Alternatively you can change the interpreter path in order to match the desidered one (i.e. /bin/python) and execute it directly (like: ./my_test_server.py of course after giving the execute permission with «chmod +x my_test_server.py»)

  Simple echo server:

  This simple server listens on a port and waits for one connection, when a client is connected it gets a chunk of data and resend it to the client, until data received is null (i.e. client presses the ENTER key)

  #!/usr/bin/env python3 # Echo server import socket HOST = '' # all available interfaces PORT = 5005 # any port > 1023 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((HOST, PORT)) s.listen(1) # 1 means the number of accepted connections conn, addr = s.accept() # waits for a new connection print('Client connected: ', addr) while True: data = conn.recv(1024) if not data: break conn.sendall(data) conn.close()

  Simple echo client

  The client connects the same server port and accepts user input until input data is null (i.e. ENTER key pressed). Any input data is converted to string and sent to the server as bytes, then waits to receive data from server, then prints echoed data to console.

  #!/usr/bin/env python3 # Echo client import socket HOST = '' # all available interfaces PORT = 5005 # any port > 1023 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((HOST, PORT)) print('Client connected.') while True: user_input = str(input()) # convert input to string if not user_input: # i.e. enter key pressed break s.sendall(user_input.encode()) # encode needed to transform string to bytes data = s.recv(1024) if not data: break print("Data received from server: ", data.decode('utf-8')) # decode needed to convert data to string

  Echo server allowing multiple connections

  The first echo server can be improved allowing multiple connections. The accept() method blocks the current execution. We can send the accepted connection to a separate thread that will manage the task with the given client, while then the main socket can be ready again to accept a new client.
  In order to stop the server gracefully, we will set the stop_main_thread variable and in order to unlock the accept() method we will send a dummy connection request.

  #!/usr/bin/env python3 # Echo server import socket import threading HOST = '' # all available interfaces PORT = 5005 # any port > 1023 main_socket: socket.socket = None stop_main_thread = False def on_client_connected(conn: socket.socket, addr): print('Client connected: ', addr) while True: data = conn.recv(1024) if not data: break conn.sendall(data) conn.close(); print('Client disconnected: ', addr) def start_server(): s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((HOST, PORT)) s.listen(10) # 10 means the number of accepted connections global main_socket global stop_main_thread main_socket = s print(f'Server started on port , waiting for connections. (Press ENTER key to stop)') while True and not stop_main_thread: try: conn, addr = s.accept() # waits for a new connection threading.Thread(target=on_client_connected, args=(conn, addr)).start() except: pass print('Server stopped.') def stop_server(): global stop_main_thread stop_main_thread = True # makes a dummy connection just to unlock accept method and trigger the gracefully stop socket.socket(socket.AF_INET, socket.SOCK_STREAM).connect((HOST, PORT)) main_thread = threading.Thread(target=start_server) main_thread.start() while True: user_input = input() if not user_input: # i.e. enter key pressed break print('Stopping server. ') stop_server() main_thread.join() main_socket.close()

  You can use the same client to connect to this server.
  This is just a simple example and it can be improved a lot, i.e. my managing sent ad received data chunks in a better way.

  Источник