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POhowto program protocol buffer in python to send messages via socket
 

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  1. POhowto program protocol buffer in python to send messages via socket
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    <p>I'm trying to use protocol buffer in python to send a message from one to another computer. I learned from a few online examples, and tried to make a minimum example out of them. However, in my code, the server does not print out the correct values of the variables the client sends. Any help is very much appreciated.</p> <p>First, test_msg.proto is as follows:</p> <pre><code>message test_msg { required int32 param1 = 1; required int32 param2 = 2; } </code></pre> <p>Second, client code (test_client.py)</p> <pre><code>from test_msg_pb2 import test_msg import socket import sys import struct address = ('localhost', 6005) client_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) client_socket.connect(address) data = test_msg() num_retransmits = 0 while(num_retransmits &lt; 10): # send the same message 10 times num_retransmits = num_retransmits + 1 data.param1 = 100 data.param2 = 5 s = data.SerializeToString() totallen = 4 + len(s) pack1 = struct.pack('&gt;I', totallen) # the first part of the message is length client_socket.sendall(pack1 + s) print "[client] param1: ", data.param1, " param2: ", data.param2 </code></pre> <p>Third, the server code (test_server.py)</p> <pre><code>from test_msg_pb2 import test_msg import socket import sys import struct address = ('localhost', 6005) server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) server_socket.bind(address) while(1): print "Listening" totallen = server_socket.recv(4) totallenRecv = struct.unpack('&gt;I', totallen)[0] messagelen = totallenRecv - 4 message = server_socket.recv(messagelen) msg = test_msg() msg.ParseFromString(message) print "[server] param1:", msg.param1, "param2:", msg.param2 </code></pre> <p>Then, after starting the server, I executing the client and it print out the following 10 lines as it send the param 10 times</p> <pre><code>[client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 [client] param1: 100 param2: 5 </code></pre> <p>However, on the server side, it prints out</p> <pre><code>Listening [server] param1: 0 param2: 0 Listening [server] param1: 0 param2: 0 Listening [server] param1: 0 param2: 0 Listening [server] param1: 0 param2: 0 Listening [server] param1: 0 param2: 0 Listening </code></pre> <p>So, the unpacked number param1 and param2 are incorrect, and it received the message only half of the times. Thanks so much for your help.</p>
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