Python network programming to verify the legitimacy of the client link

Six. More methods of socket introduction

The server socket function 
s.bind() binds (host, port number) to the socket 
s.listen() starts TCP listening 
s.accept() b passively receives connections from TCP clients, (blocking) waits for connections The arrival of the 

client socket function 
s.connect() actively initializes the TCP server connection 
s.connect_ex() An extended version of the connect() function that returns an error code when an error occurs, instead of throwing an exception 

public-purpose socket function 
s .recv() receive TCP data 
s.send() send TCP data 
s.sendall() send TCP data 
s.recvfrom() receive UDP data 
s.sendto() send UDP data 
s.getpeername() connect to the current socket s.getsockname() address of the 
current socket 
s.getsockopt() returns the parameters of the specified socket 
s.setsockopt() sets the parameters of the specified socket 
s.close() closes the socket 

facing Locked socket methods 
s.setblocking() Set the blocking and non-blocking mode of the 
socket s.settimeout() Set the timeout for blocking socket operations
s.gettimeout() Get the timeout for blocking socket operations 

File-oriented socket functions 
s.fineno() The file descriptor of the socket 
s.makefile() Create a file 

sned associated with the socket And the return value of the sendall method 
send() is the number of bytes sent, which may be less than the number of bytes of the string to be sent, which means that it may not be possible to send all the data in the string. If there is an error, an exception will be thrown 
sendall() tries to send all the data of the string, returns None if successful, and throws an exception if it fails. So the following two codes are equivalent: 

#sock.sendall('Hello world\n') 

#buffer = 'Hello world\n' 
#while buffer: 
# bytes = sock.send(buffer) 
# buffer = buffer[bytes :]

7. Verify the legitimacy of the client link

If you want to implement a simple client link authentication function in a distributed system, which is not as complicated as SSL, then use hmac+salt to implement it

Server:

from socket import *
import hmac, os

secret_key = b'linhaifeng bang bang bang'


def conn_auth(conn): # Authenticate client connections
    print('Start verifying the legitimacy of the new link')
    msg = os.urandom(32) # random number length
    conn.sendall(msg) # Send random number length
    h = hmac.new(secret_key, msg)
    digest = h.digest()
    respone = conn.recv(len(digest)) # Encrypted random number length
    return hmac.compare_digest(respone, digest)


def data_handler(conn, bufsize=1024):
    if not conn_auth(conn):
        print('The link is invalid, close it')
        conn.close()
        return
    print('The link is valid, start communication')
    while True:
        data = conn.recv(bufsize)
        if not data: break
        conn.sendall(data.upper())


def server_handler(ip_port, bufsize, backlog=5):
    tcp_socket_server = socket(AF_INET, SOCK_STREAM)
    tcp_socket_server.bind(ip_port)
    tcp_socket_server.listen(backlog)
    while True:
        conn, addr = tcp_socket_server.accept()
        print('New connection (%s:%s)' % (addr[0], addr[1]))
        data_handler(conn, bufsize)

 Client:

from socket import *
import hmac,os
secret_key = b'linhaifeng bang bang bang'
def conn_auth(conn):
    msg = conn.recv(32)
    h = hmac.new(secret_key,msg)
    digest = h.digest()
    conn.sendall(digest)
def client_handler(ip_port,bufsize=1024):
    tcp_socket_client = socket(AF_INET,SOCK_STREAM)
    tcp_socket_client.connect(ip_port)
    conn_auth(tcp_socket_client)
    while True:
        data = input('>>>').strip()
        if not data: continue
        if data == 'quit': break
        tcp_socket_client.sendall(data.encode('utf-8'))
        respone = tcp_socket_client.recv(bufsize)
        print(respone.decode('utf-8'))
    tcp_socket_client.close()
if __name__ == '__main__':
    ip_port = ('127.0.0.1',9999)
    bufsize = 1024
    client_handler(ip_port,bufsize)