add example tcp/udp communication using socket

socket/TcpClient.py

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+import socket
+import sys
+
+# Create a TCP/IP socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+# Connect the socket to the port where the server is listening
+server_address = ('localhost', 10000)
+print >>sys.stderr, 'connecting to %s port %s' % server_address
+sock.connect(server_address)
+
+try:    
+    # Send data
+    message = 'This is the message.  It will be repeated.'
+    print >>sys.stderr, 'sending "%s"' % message
+    sock.sendall(message)
+
+    # Look for the response
+    amount_received = 0
+    amount_expected = len(message)
+    
+    while amount_received < amount_expected:
+        data = sock.recv(16)
+        amount_received += len(data)
+        print >>sys.stderr, 'received "%s"' % data
+
+finally:
+    print >>sys.stderr, 'closing socket'
+    sock.close()

socket/TcpServer.py

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+import socket
+import sys
+
+# Create a TCP/IP socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+# Bind the socket to the port
+server_address = ('localhost', 10000)
+print >>sys.stderr, 'starting up on %s port %s' % server_address
+sock.bind(server_address)
+
+# Listen for incoming connections
+sock.listen(1)
+
+while True:
+    # Wait for a connection
+    print >>sys.stderr, 'waiting for a connection'
+    connection, client_address = sock.accept()
+
+    try:
+        print >>sys.stderr, 'connection from', client_address
+
+        # Receive the data in small chunks and retransmit it
+        while True:
+            data = connection.recv(1024)
+            print >>sys.stderr, 'received "%s"' % data
+            if data:
+                print >>sys.stderr, 'sending data back to the client'
+                connection.sendall(data)
+            else:
+                print >>sys.stderr, 'no more data from', client_address
+                break
+            
+    finally:
+        # Clean up the connection
+        connection.close()

socket/UdpClient.py

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+import socket
+import sys
+
+# Create a UDP socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+server_address = ('localhost', 10000)
+message = 'This is the message.  It will be repeated.'
+
+try:
+
+    # Send data
+    print >>sys.stderr, 'sending "%s"' % message
+    sent = sock.sendto(message, server_address)
+
+    # Receive response
+    print >>sys.stderr, 'waiting to receive'
+    data, server = sock.recvfrom(4096)
+    print >>sys.stderr, 'received "%s"' % data
+
+finally:
+    print >>sys.stderr, 'closing socket'
+    sock.close()

socket/UdpMulticastReceiver.py

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+import socket
+import struct
+import sys
+
+multicast_group = '224.3.29.71'
+server_address = ('', 10000)
+
+# Create the socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+# Bind to the server address
+sock.bind(server_address)
+
+# Tell the operating system to add the socket to the multicast group
+# on all interfaces.
+group = socket.inet_aton(multicast_group)
+mreq = struct.pack('4sL', group, socket.INADDR_ANY)
+sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
+
+# Receive/respond loop
+while True:
+    print >>sys.stderr, '\nwaiting to receive message'
+    data, address = sock.recvfrom(1024)
+    
+    print >>sys.stderr, 'received %s bytes from %s' % (len(data), address)
+    print >>sys.stderr, data
+
+    print >>sys.stderr, 'sending acknowledgement to', address
+    sock.sendto('ack', address)

socket/UdpMulticastSender.py

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+import socket
+import struct
+import sys
+
+message = 'very important data'
+multicast_group = ('224.3.29.71', 10000)
+
+# Create the datagram socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+# Set a timeout so the socket does not block indefinitely when trying
+# to receive data.
+sock.settimeout(0.2)
+
+# Set the time-to-live for messages to 1 so they do not go past the
+# local network segment.
+ttl = struct.pack('b', 1)
+sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl)
+
+try:
+
+    # Send data to the multicast group
+    print >>sys.stderr, 'sending "%s"' % message
+    sent = sock.sendto(message, multicast_group)
+
+    # Look for responses from all recipients
+    while True:
+        print >>sys.stderr, 'waiting to receive'
+        try:
+            data, server = sock.recvfrom(16)
+        except socket.timeout:
+            print >>sys.stderr, 'timed out, no more responses'
+            break
+        else:
+            print >>sys.stderr, 'received "%s" from %s' % (data, server)
+
+finally:
+    print >>sys.stderr, 'closing socket'
+    sock.close()

socket/UdpServer.py

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+import socket
+import sys
+
+# Create a TCP/IP socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+# Bind the socket to the port
+server_address = ('localhost', 10000)
+print >>sys.stderr, 'starting up on %s port %s' % server_address
+sock.bind(server_address)
+
+while True:
+    print >>sys.stderr, '\nwaiting to receive message'
+    data, address = sock.recvfrom(4096)
+    
+    print >>sys.stderr, 'received %s bytes from %s' % (len(data), address)
+    print >>sys.stderr, data
+    
+    if data:
+        sent = sock.sendto(data, address)
+        print >>sys.stderr, 'sent %s bytes back to %s' % (sent, address)