• Address Family
  • AF_INET, IPv4 address
  • AF_INET6, IPv6 address
  • AF_UNIX, Unix Domain Socket, an interprocess communication protocol
• Socket Type
  • SOCK_DGRAM, UDP
  • SOCK_STREAM, TCP/IP
• Useful Functions
  • getfqdn(), get a fully qualified domain name, which is a domain name that specifies its exact location in the tree hierarchy of the DNS
  • gethostname(), get the host name of the current system
  • gethostbyname(), get IPv4 address from host name
  • gethostbyname_ex(), get host name, aliases, addresses
  • gethostbyaddr(), get host name, aliases, and addresses by IP address
  • getnameinfo(), translate socket address (host, port) to domain name and protocol
  • getservbyname(), translate an internet service name to port number

#!/usr/bin/python
 
import socket
 
#DNS
print socket.getfqdn('www.google.com');
print socket.gethostname();
print socket.gethostbyname('localhost');
print socket.gethostbyname('www.google.com');
print socket.gethostbyname_ex('localhost');
print socket.gethostbyaddr('4.2.2.2');
print socket.getnameinfo((socket.gethostbyname('www.google.com'), 80), 0);
print socket.getservbyname('http');
print socket.getservbyport(80);
print socket.getaddrinfo("www.google.com", 80, 0, 0, socket.IPPROTO_TCP)
print socket.getdefaulttimeout();
			

• Client, get string from standard input, send it to server, then receive the feedback from server and print it to standard output
• Server, receive string from client, convert it to upper case, then send it back to client

#server.py
#!/usr/bin/python
 
import socket
 
HOST = '' # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
 
# Create a socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# Bind the socket to an address
s.bind((HOST, PORT))
 
# Waiting for a connection
s.listen(2)
print 'Waiting for a connection ...'
 
while 1:
    # Build a connection, create a new socket to handle it, get the client address
    conn, addr = s.accept()
    print 'Connecting server at: ', conn.getsockname(),
    print 'from client at: ', addr
    try:
        data = conn.recv(1024)
        print 'Received: ', data;
        #if not data: break
        conn.sendall(data.upper())
    except socket.error, msg:
        print "Error: ", msg;
        break
conn.close()
			

#client.py
#!/usr/bin/python
 
import socket
 
# Server address
HOST = ''    # The remote host
PORT = 50007              # The same port as used by the server
 
# Create a socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 
# Build a connection
s.connect((HOST, PORT))
 
# Read the message from keyboard
m = raw_input("Eneter your message:\n");
while len(m) < 1:
    m = raw_input("Not allow empty message, please re-input your message:\n");
#m = input("Eneter your message:\n");# evaluate the string
 
# Send the message to server
s.send(m);
#s.sendall('Hello, world')
 
# Receive the feedback from server
data = s.recv(1024)
s.close()
 
print 'Received from server:\n', data
#print 'Received:\n', repr(data)
 
			

• the address of the socket is a path on the filesystem, rather than a tuple containing servername and port
• the node created in the filesystem to represent the socket persists after the socket is closed, and needs to be removed each time the server starts up

#server.py
#!/usr/bin/python
 
import socket
import sys
import os
 
server_address = './uds_socket'
 
# Make sure the socket does not already exist
try:
    os.unlink(server_address)
except OSError:
    if os.path.exists(server_address):
        raise
 
# Create a socket
s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
print 'Socket name: ', s.getsockname();
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# Bind the socket to an address
s.bind(server_address)
 
# Waiting for a connection
s.listen(1)
print 'Waiting for a connection ...'
 
while 1:
    # Build a connection, create a new socket to handle it, get the client address
    conn, addr = s.accept()
    print 'Connecting server at: ', conn.getsockname(),
    print 'from client at: ', addr
    try:
        data = conn.recv(1024)
        print 'Received: ', data;
        #if not data: break
        conn.sendall(data.upper())
    except socket.error, msg:
        print "Error: ", msg;
        break
conn.close()
			

#client.py
#!/usr/bin/python
 
import socket
 
# Create a socket
s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 
server_address = './uds_socket'
 
# Build a connection
s.connect(server_address)
 
# Read the message from keyboard
m = raw_input("Eneter your message:\n");
while len(m) < 1:
    m = raw_input("Not allow empty message, please re-input your message:\n");
#m = input("Eneter your message:\n");# evaluate the string
 
# Send the message to server
s.send(m);
#s.sendall('Hello, world')
 
# Receive the feedback from server
data = s.recv(1024)
s.close()
 
print 'Received from server:\n', data
#print 'Received:\n', repr(data)
			

• No connection
• Use sendto

#server.py
#!/usr/bin/python
 
import socket;
 
port = 50007;
 
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 
s.bind(('', port))
 
print 'UDP server ...'
 
while 1:
    data, addr = s.recvfrom(1024)
    print 'server received %r from %r' % (data, addr)
    s.sendto(data.upper(), addr); #the socket should not be connected to a remote socket
			

#client.py
#!/usr/bin/python
 
import socket
 
# Server address
HOST = '' # The remote host
PORT = 50007 # the port of the server
 
# Create a socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 
# Read the message from keyboard
m = raw_input("Eneter your message:\n");
while len(m) < 1:
    m = raw_input("Not allow empty message, please re-input your message:\n");
#m = input("Eneter your message:\n");# evaluate the string
 
# Send the message to server
s.sendto(m, (HOST, PORT));
 
# Receive the feedback from server
data = s.recv(1024)
s.close()
 
print 'Received from server:\n', data
#print 'Received:\n', repr(data)
			

#server.py
#!/usr/bin/python
 
import binascii
import socket
import struct
import sys
 
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = ('localhost', 10000)
sock.bind(server_address)
sock.listen(1)
 
# Create Struct instance
s = struct.Struct('hhl');
 
while True:
    print >>sys.stderr, '\nwaiting for a connection'
    connection, client_address = sock.accept()
    try:
        data = connection.recv(s.size)
        print >>sys.stderr, 'received "%s"' % binascii.hexlify(data)
 
        unpacked_data = s.unpack(data)
        print >>sys.stderr, 'unpacked:', unpacked_data
    finally:
        connection.close();
			

#!/usr/bin/python
 
import socket
import struct
import binascii
 
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = ('localhost', 10000)
sock.connect(server_address)
 
# Create Struct instance
s = struct.Struct('hhl');
 
# Pack information
packed = s.pack(1, 2, 3);#pack data into a string
sock.sendall(packed)
			

#server.py TCP
#!/usr/bin/python
 
import binascii
import socket
import struct
import sys
import time
 
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_address = ('localhost', 10000)
sock.bind(server_address)
sock.listen(1)
 
# Create Struct instance
s = struct.Struct('f');
connection, client_address = sock.accept()
 
num = 0;
 
while True:
    try:
        data = connection.recv(s.size)
        unpacked_data = s.unpack(data)
        num += 1;
        print 'Received: ', num, unpacked_data
	time.sleep(0.01)
    except Exception, err:
        print err
        break;
 
connection.close();
			

#client.py TCP
#!/usr/bin/python
 
import socket
import struct
import binascii
import random
 
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = ('localhost', 10000)
sock.connect(server_address)
 
# Create Struct instance
s = struct.Struct('f');
 
num = 0;
 
# Pack information
while True:
    n = random.random();
    packed = s.pack(n);#pack data into a string
    sock.sendall(packed)
    num += 1;
    print 'Sent: ', num, n
			

#server.py UDP
#!/usr/bin/python
 
import binascii
import socket
import struct
import sys
import time
 
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_address = ('localhost', 10000)
sock.bind(server_address)
 
# Create Struct instance
s = struct.Struct('f');
 
num = 0;
 
while True:
    try:
        data, address= sock.recvfrom(s.size)
        unpacked_data = s.unpack(data)
        num += 1;
        print 'Received: ', num, unpacked_data
        time.sleep(0.001)
    except Exception, err:
        print err
        break;
			

#client.py UDP
#!/usr/bin/python
 
import socket
import struct
import binascii
import random
 
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_address = ('localhost', 10000)
 
# Create Struct instance
s = struct.Struct('f');
 
num = 0;
 
# Pack information
while True:
    n = random.random();
    packed = s.pack(n);#pack data into a string
    sock.sendto(packed, server_address)
    num += 1;
    print 'Sent: ', num, n