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Client - Server socket programming with python

Below are my three scripts. I need to send the message from sricpt 1(Sensor.py) to script 2.(Client.py). And then the script 2 should send the message to script 3(Server.py).
It works fine till script 2 but the message isn't being received at the script 3 and the recvfrom() keeps waiting. There is no error but the script 3 doesn't show the message. Im using UDP. Please help.
SCRIPT 1(Sensor.py)
from socket import *
from time import ctime
CLIENT_IP = '192.168.1.109'
PORT = 23567
BUFSIZE = 1024
ADDR = (CLIENT_IP, PORT)
udpCliSock = socket(AF_INET, SOCK_DGRAM)
while True:
sendData = input("> ")
if sendData is None:
break
udpCliSock.sendto(sendData.encode(), ADDR)
udpCliSock.close()
SCRIPT 2(Client.py)
from socket import *
from time import ctime
HOST = '192.168.1.103'
CLIENT_IP='192.168.1.109'
PORT = 5005
SENSOR_PORT_NO=23567
BUFSIZE = 1024
ADDR = (HOST, PORT)
CLIENT_ADDR=(CLIENT_IP,SENSOR_PORT_NO)
udpCliSock = socket(AF_INET, SOCK_DGRAM)
client = socket(AF_INET, SOCK_DGRAM)
client.bind(CLIENT_ADDR)
while True:
print("...waiting for response...")
#recv_data, ADDR = udpCliSock.recvfrom(BUFSIZE)
recv_data, ADDR = client.recvfrom(1024)
if recv_data is not None:
recv_data = recv_data.decode()
print("[%s]: receiving data from server %s:%s :%s" % (ctime(),ADDR[0], ADDR[1], recv_data))
sendData = recv_data
udpCliSock.sendto(sendData.encode(), ADDR)
udpCliSock.close()
SCRIPT 3(Server.py)
from socket import *
from time import ctime
HOST = '192.168.1.103'
PORT = 5005
BUFSIZE = 1024
ADDR = (HOST, PORT)
udpSerSock = socket(AF_INET, SOCK_DGRAM)
udpSerSock.bind(ADDR)
while True:
print("...waiting for message...")
data, ADDR = udpSerSock.recvfrom(BUFSIZE)
print(data.decode)
if data is None:
break
print("[%s]: From Address %s:%s receive data: %s" % (ctime(),ADDR[0],ADDR[1], data.decode()))
udpSerSock.close()

The problem is that, in the Client.py, you are overwriting the address of the server when you receive the datagram from the sensor. Here:
recv_data, ADDR = client.recvfrom(1024)
ADDR starts out with the server's socket address, but this function overwrites that variable with the sensor's socket address. So when you try to send, you're sending it back to the sensor (who of course isn't ever receiving it).
A better method is to connect that socket to the server at the beginning. Then you can just use send instead of sendto since the address won't be changing. Should work after that:
...
udpCliSock = socket(AF_INET, SOCK_DGRAM)
udpCliSock.connect(ADDR) # <<<<<<===============
client = socket(AF_INET, SOCK_DGRAM)
client.bind(CLIENT_ADDR)
while True:
print("...waiting for response...")
recv_data, addr = client.recvfrom(1024)
if recv_data is not None:
recv_data = recv_data.decode()
print("[%s]: receiving data from server %s:%s :%s" % (ctime(),addr[0], addr[1], recv_data))
sendData = recv_data
udpCliSock.send(sendData.encode()) # <<<<<<===============
udpCliSock.close()

python socket : server must send a message before recv

In socket, I found that if server does not send any message before call recv(), server will be no response, whatever using mutilthread or not.
As the figure shows below:
enter image description here
enter image description here
server.py(Using SocketServer module):
def handle(self):
conn = self.request
# conn.send('Welcome to server')
flag = True
while flag:
data = conn.recv(1024)
print 'client:' + data
if data == 'exit':
flag = False
conn.send('AAAAAA')
conn.close()
client.py:
client = socket.socket()
ip_port = ('127.0.0.1', 11111)
client.connect(ip_port)
while True:
data = client.recv(1024)
print 'server:' + data
send = raw_input('client:')
client.send(send)
if send == 'exit':
sys.exit()
I would appreciate it very much if you would help me with it.

# server.py
import socket
TCP_IP = '127.0.0.1'
TCP_PORT = 5005
BUFFER_SIZE = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP, TCP_PORT))
s.listen(1)
conn, addr = s.accept()
print 'Connection address:', addr
while 1:
data = conn.recv(BUFFER_SIZE)
if not data: break
print "Server received data:", data
conn.send("Data received at server side")
conn.close()
# client.py
import socket
TCP_IP = '127.0.0.1'
TCP_PORT = 5005
BUFFER_SIZE = 1024
MESSAGE = "Hello World!"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
s.send(MESSAGE)
print "Client: " + MESSAGE
data = s.recv(BUFFER_SIZE)
s.close()
print data
I think providing a sample code could speak itself.
# Expected input:
python server.py
python client.py
# Expected output:
# (server output)
Connection address: ('127.0.0.1', 62136)
Server received data: Hello World!
# (client output)
Client: Hello World!
Data received at server side
You could find out your missing component by comparing the code,such as bind().
Hope it help.
With reference to this site: https://wiki.python.org/moin/TcpCommunication

python 3.4.3 file is not writing completly

The following is complete client , server and sendproc codes:
Client.py
from socket import *
import pickle
import sendproc
import struct
s = socket(AF_INET, SOCK_STREAM) # Create a socket object
host = "192.168.1.4" # Get local machine name
port = 1094 # Reserve a port for your service.
s.connect((host, port))
with open("file.txt",'rb') as f:
print ('file opened')
print('Sending file...')
for data in f:
print(data)
print("MSG sent")
sendproc.send_msg(s, data)
Server.py
from socket import *
import pickle
import sendproc
port = 1094 # Reserve port for service.
s = socket(AF_INET,SOCK_STREAM) # Create a socket object
host = "192.168.1.4" # Get local machine name
s.bind((host, port)) # Bind to the port
s.listen(5)
print('server is listening')
conn,addr = s.accept()
with open("file1.txt",'w') as fb:
print("File downloading\n",fb)
while True:
print("hi")
data = sendproc.recv_msg(conn)
print(data)
if not data:
print("No data")
break
fb.write(data)
fb.flush()
print("Download complete\n")
SendRecieveProcedure.py
import struct
def send_msg(s, msg):
msg2 = struct.pack('>I', len(msg)) + msg
s.send(msg2)
def recv_msg(s):
# Read message length and unpack it into an integer
raw_msglen = s.recv(4)
print(raw_msglen)
if not raw_msglen:
return None
n = struct.unpack('>I',raw_msglen)[0]
# Read the message data
data = ' '
while len(data) < n:
packet = s.recv(n - len(data)).decode("cp437")
if not packet:
return None
data += packet
#print("hwllo",data )
return data
output prints correctly to the console, but if I go open up the file it's only writing starting lines.so what is the problem in code

Python socket server receive image

I am trying to receive an image from Android to PC using socket in Python. My server code is as follows:
import socket
address = ("10.0.0.12", 5000)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(address)
s.listen(1000)
client, addr = s.accept()
print 'got connected from', addr
filename = open('tst.jpg', 'wb')
while True:
strng = client.recv(1024)
if not strng:
break
filename.write(strng)
filename.close()
print 'received, yay!'
client.close()
And it returns me a tst.jpg which is the same size of that on my Android. But I cannot open the pic.
Here is my Android code:
Socket photoSocket = new Socket(ipString, port);
DataOutputStream dos = new DataOutputStream(photoSocket.getOutputStream());
FileInputStream fis = new FileInputStream(PhotoActivity.filePath);
int size = fis.available();
byte[] data = new byte[size];
fis.read(data);
dos.writeInt(size);
dos.write(data);
dos.flush();
dos.close();
fis.close();
photoSocket.close();

so the android code is sending the size as int in front of the data, but the python code doesn't read it.
import socket
import struct
address = ("10.0.0.12", 5000)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(address)
s.listen(1000)
client, addr = s.accept()
print 'got connected from', addr
buf = ''
while len(buf)<4:
buf += client.recv(4-len(buf))
size = struct.unpack('!i', buf)
print "receiving %s bytes" % size
with open('tst.jpg', 'wb') as img:
while True:
data = client.recv(1024)
if not data:
break
img.write(data)
print 'received, yay!'
client.close()

Cannot Get Strings Across in a Socket Program

I have been looking at some code for a small chat program that I found online. It was originally written for 2.7, but it seems to work with 3.2. The only problem is that I cannot send strings, only numbers:
The chat.py file source code:
from socket import *
HOST = ''
PORT = 8000
s = socket(AF_INET, SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print ('Connected by ' + str(addr))
i = True
while i is True:
data = conn.recv(1024)
print ("Received " + repr(data))
reply = str(input("Reply: "))
conn.send(reply)
conn.close()
And the client.py source file:
from socket import *
HOST = ''
PORT = 8000
s = socket(AF_INET, SOCK_STREAM)
s.connect((HOST, PORT)) # client-side, connects to a host
while True:
message = str(input("Your Message: "))
s.send(message)
print ("Awaiting reply...")
reply = s.recv(1024) # 1024 is max data that can be received
print ("Received " + repr(reply))
s.close()
When I run these using two separate terminals, they work, but do not send strings.
Thank you

When you work with sockets, the message you're passing around should probably be in bytes, b'bytes'. In Python 2.x, a str is actually what a bytes is in Python 3.x
So your message should be something like:
message = b'Message I want to pass'
Check here http://docs.python.org/3.3/library/stdtypes.html for more information.
According to http://docs.python.org/3/library/functions.html#input input returns a str, which means you'll have to encode message into bytes as such:
message = message.encode()
Do verify that this is the right approach to convert str to bytes by checking the type of message.

Your socket code is correct, it was just failing due to an unrelated error due to raw_input vs input. You probably intended to read a string from the shell instead of reading a string and trying to evaluate it as Python code which is what input does.
Try this instead:
chat.py
from socket import *
HOST = ''
PORT = 8000
s = socket(AF_INET, SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print ('Connected by ' + str(addr))
i = True
while i is True:
data = conn.recv(1024)
print ("Received " + repr(data))
reply = str(raw_input("Reply: "))
conn.send(reply)
conn.close()
client.py
from socket import *
HOST = ''
PORT = 8000
s = socket(AF_INET, SOCK_STREAM)
s.connect((HOST, PORT)) # client-side, connects to a host
while True:
message = str(raw_input("Your Message: "))
s.send(message)
print ("Awaiting reply...")
reply = s.recv(1024) # 1024 is max data that can be received
print ("Received " + repr(reply))
s.close()