We Keep Coding

weird movement socket based programming [duplicate]

I copied the echo server example from the python documentation and it's working fine. But when I edit the code, so it wont send the data back to the client, the socket.recv() method doesn't return when it's called the second time.
import socket
HOST = ''
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(b'ok')
conn.close()
In the original version from the python documentation the while loop is slightly different:
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
Client's code:
import socket
HOST = 'localhost'
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
data = s.recv(1024)
s.close()
print('Received', repr(data))

TCP sockets are streams of data. There is no one-to-one correlation between send calls on one side and receive calls on the other. There is a higher level correlation based on the protocol you implement. In the original code, the rule was that the server would send exactly what it received until the client closed the incoming side of the connection. Then the server closed the socket.
With your change, the rules changed. Now the server keeps receiving and discarding data until the client closes the incoming side of the connection. Then the server sends "ok" and closes the socket.
A client using the first rule hangs because its expecting data before it closes the socket. If it wants to work with this new server rule, it has to close its outgoing side of the socket to tell the server its done, and then it can get the return data.
I've updated the client and server to shutdown parts of the connection and also have the client do multiple recv's in case the incoming data is fragmented. Less complete implementations seem to work for small payloads because you are unlikely to get fragmentation, but break horribly in real production code.
server
import socket
HOST = ''
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(b'ok')
conn.shutdown(socket.SHUT_WR)
conn.close()
client
import socket
HOST = 'localhost'
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
s.shutdown(socket.SHUT_WR)
data = b''
while True:
buf = s.recv(1024)
if not buf:
break
data += buf
s.close()
print('Received', repr(data))

The number of receive and send operations have to match because they are blocking. This is the flow diagram for your code:
Server listen
Client connect
Server receive (this waits until a message arrives at the server) [1]
Client send 'Hello world' (received by [1])
Server receive (because there was data received) [2]
Client receive [3]
Because the server and the client are blocked now, no program can continue any further.
The fix would be to remove the client's receive call because you removed the server's send call.

TCP client server not receiving any data from each other

I have written the following TCP client and server using python socket module. However, after I run them, no output is being given. It seems that
the program is not able to come out of the while loop in the recv_all method
Server:
import socket
def recv_all(sock):
data = []
while True:
dat = sock.recv(18)
if not dat:
break
data.append(dat)
return "".join(data)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
HOST = '127.0.0.1'
PORT = 45678
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((HOST, PORT))
sock.listen(1)
print "listening at", sock.getsockname()
while True:
s, addr = sock.accept()
print "receiving from", addr
final = recv_all(s)
print "the client sent", final
s.sendall("hello client")
s.close()
Client :
import socket
def recv_all(sock):
data=[]
while True:
dat=sock.recv(18)
if not dat:
break
data.append(dat)
return "".join(data)
sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
PORT=45678
HOST='127.0.0.1'
sock.connect((HOST,PORT))
sock.sendall("hi server")
final=recv_all(sock)
print "the server sent",final

Because in server file you use an endless loop in another. I suggest you to edit recv_all method in both files this way:
def recv_all(sock):
data = []
dat = sock.recv(18)
data.append(dat)
return "".join(data)
But after edit like this your server stays on until KeyInterrupt, while you should run client file everytime you want to send data. If you want an automatically send/receive between server and client, I offer you try threading.

Setting up UDP client (python)

I tried to set up a UDP client and see if I can print the data like below:
import socket
target_host = "127.0.0.1"
target_port = 80
# create a socket object
client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
#send some data
client.sendto("AAABBBCCC", (target_host, target_port))
#receive some data
data, addr = client.recvfrom(4096)
print data
So I execute it with
$python udp_client.py
But then the shell just stuck at this line in the code
data, addr = client.recvfrom(4096)
How to solve this problem?

python udp server parse and send received data to MySQL

i am working on some proof of concept study research project and have python udp socket server that listen received data.
Client send data NAME and FAMILY NAME on UDP to server.
I would like to receive that data on UDP socket server side and on receive send this data to mysql database with two fields f_name and l_name.
import socket
UDP_IP = "192.168.1.10"
UDP_PORT = 9000
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind((UDP_IP, UDP_PORT))
print "UDP SERVER STARTED!"
while True:
data, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print "MSG Received:", data
this example is taken from web and with this server i get data on console.
I would like to have it like below and of course code/concept can be changed. This might be solved with scapy sniffer but that would be dirty.
Conceptually i would like to have ti something like:
1. socekt server received data
2. parse data received and send this data to mysql
I started with this in mind but doesnt work
import socket
import MySQLdb
UDP_IP = "192.168.1.10"
UDP_PORT = 9000
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind((UDP_IP, UDP_PORT))
print "UDP SERVER STARTED!"
while True:
data, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print "received message:", data
def parse(data):
db = MySQLdb.connect("localhost","db_user","db_pass","directory_db")
cursor = db.cursor()
# Params to insert into DB
f_nameObj = re.search(r'NAME: (.*?) .*', data, re.M|re.I)
if f_name:
f_name = f_nameObj.group(1)
l_nameObj = re.search(r'SURNAME: (.*?) .*', data, re.M|re.I)
if l_name:
l_name = l_nameObj.group(1)
# MySQL EXECUTION
cursor.execute("""
INSERT INTO dictionary (f_name, l_name) VALUES (%s, %s)""",(f_name,l_name))
#
db.commit()
With this kind of udp server i see no messages so seems function that parse data is not working with server.
Any help or guidance would be appreciated

In your server when you receive data you don't call parse function.You just print the content of data. Add the line with the comment and see the result.
while True:
data, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print "received message:", data
parse(data) # Call the Function

client-server chat python error

I'm trying the following client and server chat program. Although I get an error whenever I try to run the server program, when the client program runs it stays on a blank screen not allowing me to type anything. I've tried running server first and running client first and I get the same results. I can't read the error from the server program because it flashes the error and closes the window. Here is my code:
server:
#server
import socket
import time
HOST = ''
PORT = 8065
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind((HOST,PORT))
s.listen(1)
conn, addr = s.accept()
print 'Connected by', addr
while 1:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
conn.close()
client:
#client
import socket
import time
HOST = "localhost"
PORT = 8065
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.connect((HOST,PORT))
s.sendall('Helloworld')
data = s.recv(1024)
s.close()
print 'Recieved', repr(data)

Im not an expert but I was able to make your examples work by changing the socket from datagram to stream connection, and then encoding message being sent because strings aren't supported (although this might not effect you since I think that change was made in Python 3...I'm not 100% sure).
I believe the main issue is that you're trying to listen() but SOCK_DGRAM (UDP) doesn't support listen(), you just bind and go from there, whereas SOCK_STREAM (TCP) uses connections.
If you're just trying to get the program going, use the below code, unless there is a specific reason you'd like to use SOCK_DGRAM.
The code is below:
client
#client
import socket
import time
HOST = "localhost"
PORT = 8065
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST,PORT))
test = 'Helloworld'
s.sendall(test.encode())
data = s.recv(1024)
s.close()
print 'Recieved', repr(data)
server
#server
import socket
import time
HOST = ''
PORT = 8065
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST,PORT))
s.listen(1)
conn, addr = s.accept()
print ('Connected by', addr)
while 1:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
conn.close()