EDIT: I solved this question myself, look at the first answer if you have a similar issue
I am new to sockets and made a client-server test modifying one example, it sends and receives data ok but when closing the server get caught in a loop receiving blank messages and I can't find out why even though I use shutdown(socket.SHUT_RDWR) to close the connection immediately according to the documentation.
I had to use two cmd of windows for each one (server and client) because when running first the server in idle and then the client I got in client_example ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it here is the code. Anyways, here it is the sequence I tried:
(in the client console):
c:\python33\python client_example.py
SEND( TYPE q or Q to Quit):Hi
SEND( TYPE q or Q to Quit):q
(in the server console):
c:\python33\python server_example3.py
TCPServer Waiting for client on port 7000
I got a connection from ('127.0.0.1', 49263)
RECEIVED: b'Hi'
RECEIVED: b''
RECEIVED: b''
RECEIVED: b''
RECEIVED: b''
RECEIVED: b''
.... <---After I did CTRL+C
Traceback (most recent call last):
File "server_example.py", line 19, in <module>
print("RECEIVED:",data)
File "c:\python33\lib\encodings\cp850.py", line 19, in encode
return codecs.charmap_encode(input,self.errors,encoding_map)[0]
KeyboardInterrupt
Here is the code of the server and client:
server_example.py:
#TCP server example
import socket
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind(("", 7000))
server_socket.listen(5)
print("TCPServer Waiting for client on port 7000")
while 1:
client_socket, address = server_socket.accept()
print("I got a connection from ", address)
while 1:
data = client_socket.recv(32)
if (data == 'q' or data == 'Q'):
client_socket.shutdown(socket.SHUT_RDWR)
client_socket.close()
break;
else:
print("RECEIVED:",data)
client_example.py:
# TCP client example
import socket
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(("localhost", 7000))
while 1:
data = input( "SEND( TYPE q or Q to Quit):" )
if (data != 'Q' and data != 'q'):
my_bytes = bytearray()
for c in data:
my_bytes.append(ord(c))
client_socket.send(my_bytes)
else:
client_socket.shutdown(socket.SHUT_RDWR)
client_socket.close()
break;
Well, I feel dumb that I solved this thing after 11 minutes of posting the question when I was unable to solve it for 2 hours...
The problem was that I was comparing data with the string 'q' which was correct in python 2 but in python 3 what is being sent are bytes, b'q' <> 'q' ...
Here is the corrected code:
server_example.py
#TCP server example
import socket
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind(("", 7000))
server_socket.listen(5)
print("TCPServer Waiting for client on port 7000")
while 1:
client_socket, address = server_socket.accept()
print("I got a connection from ", address)
while 1:
data = client_socket.recv(32)
print("RECEIVED:",data)
if (data == b'q' or data == b'Q'):
## client_socket.shutdown(socket.SHUT_RDWR)
client_socket.close()
break;
break;
client_example.py
# TCP client example
import socket
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(("localhost", 7000))
while 1:
data = input( "SEND( TYPE q or Q to Quit):" )
if (data != 'Q' and data != 'q'):
my_bytes = bytearray()
for c in data:
my_bytes.append(ord(c))
client_socket.send(my_bytes)
else:
my_bytes = bytearray()
my_bytes.append(ord(data))
client_socket.send(my_bytes)
## client_socket.shutdown(socket.SHUT_RDWR)
client_socket.close()
break;
You're assuming you're going to get the Q. You should also engage in the same processing when you get EOS from read, whatever form that takes in Python.
#EJP : By EOS you mean end of stream? If so you are right, this example was a very simple one to get started in which I overlooked details like these.
Anyway I found that using this check in the server it is solved:
data = input( "SEND( TYPE q or Q to Quit):" )
if (data == b''):
break;
Related
So I'm trying to do a mock Traceroute function where a UDP packet is sent to an IP address. I'm trying to design the program in such a way where a packet is sent each time the packet makes it to a router. I am trying to do this by making a very short TTL. However, the recvfrom function is stalling.
Here's the code:
host_addr = gethostbyname(host)
port = 33434
max_hops = 30
ttl = 1
while True:
recv_socket = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)
send_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
send_socket.setsockopt(0, 4, ttl)
recv_socket.bind(("", port))
send_socket.sendto("waddup".encode(), (host_addr, port))
cur_addr = None
cur_name = None
path_end = False
cur_bytes = None
attempts_left = 3
timeReceived = 0
pingStartTime = 0
while not path_end and attempts_left > 0:
try:
pingStartTime = time.time()
cur_bytes, cur_addr = recv_socket.recvfrom(1024)
timeReceived = time.time()
path_end = True
cur_addr = cur_addr[0]
try:
cur_name = gethostbyaddr(cur_addr)[0]
except error:
cur_name = cur_addr
except error:
attempts_left -= 1
send_socket.close()
recv_socket.close()
if not path_end:
pass
if cur_addr is not None:
cur_host = "%s (%s) " % (cur_name, cur_addr)
else:
cur_host = ""
print("%d: %.0f ms " %
(
ttl,
(timeReceived - pingStartTime) * 1000,
) + cur_host
)
ttl += 1
if cur_addr == host_addr or ttl > max_hops:
break
I have set up the receiving socket for an ICMP packet as far as I can tell but it just hangs on recvfrom. I've allowed all ICMP connections on Windows Defender and when I run Wireshark, an appropriate ICMP packet is sent to my router.
The packet with the TTL expired message is the one I want to receive
I'm new to networking but all the code I've seen online has this exact setup. Would anyone be able to tell me why it's stalling and what I can do to fix it? I want the program to read the ICMP packet with the TTL expiration message.
I'm trying to make client-server connection, I don't know much about sockets etc. so I used github example for luajitsocket and im getting error "A non-blocking socket operation could not be completed immediately."
So I dont even know how can I fix that, that's why Im asking here
My code:
local port = 8080
local address = socket.find_first_address("*", port)
do -- server
local server = assert(socket.create("inet", "dgram", "udp"))
assert(server:set_blocking(false))
assert(server:bind(address))
print("hosting at ", address:get_ip(), address:get_port())
function update_server()
local data, addr = server:receive_from()
if data then
print(data)
assert(server:send_to(addr, "hello from server " .. os.clock()))
elseif addr ~= "timeout" then
error(addr)-- here
end
end
end
do -- client
local client = assert(socket.create("inet", "dgram", "udp"))
assert(client:set_blocking(false))
local next_send = 0
function update_client()
if next_send < os.clock() then
assert(client:send_to(address, "hello from client " .. os.clock()))
next_send = os.clock() + math.random() + 0.5
end
local data, addr = client:receive_from(address)
if data then
print(data, addr:get_ip(), addr:get_port())
elseif addr ~= "timeout" then
error(addr)
end
end
end
while true do
update_server()
update_client()
end
taken from: https://github.com/CapsAdmin/luajitsocket/blob/master/examples/udp_client_server.lua
I was looking about this error on google but can't find any working solution. Thanks in advance!
After set_blocking(false) that return code should not be considered abnormal.
You're probably getting it from receive_from(), which you should not be calling constantly, you should do it when select() or poll() tells you the socket has data waiting.
This is a code which is given to us by our teacher for using in our homework. There should't have been an error. But there is. Please help me fix it. (The error is in line9)
import socket
serverPort = 12000
serverSocket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
serverSocket.bind(('',serverPort))
serverSocket.listen(1)
print ("The server is ready to receive")
while 1:
connectionSocket, addr = serverSocket.accept()
byte_sentence = connectionSocket.recv(1024)
utf_sentence = byte_sentence.decode("utf-8")
modified_utf_sentence = utf_sentence.upper()
modified_byte_sentence = bytes(modified_utf_sentence, "utf-8")
connectionSocket.send(modified_byte_sentence)
connectionSocket.close()
File "tcpserver.py", line 9
connectionSocket, addr = serverSocket.accept()
^
IndentationError: expected an indented block
You need to indent your code by 4 spaces after you declare your while loop.
import socket
serverPort = 12000
serverSocket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
serverSocket.bind(('',serverPort))
serverSocket.listen(1)
print ("The server is ready to receive")
while 1:
connectionSocket, addr = serverSocket.accept()
byte_sentence = connectionSocket.recv(1024)
utf_sentence = byte_sentence.decode("utf-8")
modified_utf_sentence = utf_sentence.upper()
modified_byte_sentence = bytes(modified_utf_sentence, "utf-8")
connectionSocket.send(modified_byte_sentence)
connectionSocket.close()
everything in the while loop must be indented by 4 spaces. Returning to unindented code terminates the while looop.
I am writing a python code to find throughput between server and client. It is based on speedtest.net functionality where I am sending a dummy file to calculate the speed. The problem I am facing is unreliable throughput output. I will appreciate your suggestions on the same. Here is the code.
server.py
import socket
import os
port = 60000
s = socket.socket()
host = socket.gethostname()
s.bind((host, port))
s.listen(5)
print 'Server listening....'
while True:
conn, addr = s.accept()
print 'Got connection from', addr
data = conn.recv(1024)
print('Server received', repr(data))
filename='akki.txt'
b = os.path.getsize(filename)
f = open(filename,'rb')
l = f.read(b)
while (l):
conn.send(l)
l = f.read(b)
f.close()
print('Done sending')
conn.send('Thank you for connecting')
conn.close()
Client.py
import socket
import time
import os
s = socket.socket()
host = socket.gethostname()
port = 60000
t1 = time.time()
s.connect((host, port))
s.send("Hello server!")
with open('received_file', 'wb') as f:
print 'file opened'
t2 = time.time()
while True:
data = s.recv(1024)
if not data:
break
f.write(data)
t3 = time.time()
print data
print 'Total:', t3 - t1
print 'Throughput:', round((1024.0 * 0.001) / (t3 - t1), 3),
print 'K/sec.'
f.close()
print('Successfully received the file')
s.close()
print('connection closed')
Output when sending akki.txt
Server Output
Server listening....
Got connection from ('10.143.47.165', 60902)
('Server received', "'Hello server!'")
Done sending
Client output
file opened
Raw timers: 1503350568.11 1503350568.11 1503350568.11
Total: 0.00499987602234
**Throughput: 204.805 K/sec.**
Successfully received the file
connection closed
Output for ak.zip ( which is bigger file)
Client output
file opened
Total: 0.0499999523163
**Throughput: 20.48 K/sec.**
Successfully received the file
connection closed
Short Answer: you need to take the file size into consideration.
More Details:
Throughput is data/time. Your calculation:
round((1024.0 * 0.001) / (t3 - t1), 3)
Doesn't take the file size into account. Since sending a large file takes more time, 't3-t1' is bigger so your throughput is smaller (same numerator with larger denominator). Try adding the file size to the formula and you should get much more constant results.
Hope this helps.
I have the below code that i am trying the run using python3.2 interpreter.
import socket #for sockets
import sys #for exit
#from UserString import MutableString
#create an INET, STREAMing socket
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except socket.error:
print ('Failed to create socket')
sys.exit()
print ('Socket Created')
host = 'www.google.com';
port = 80;
try:
remote_ip = socket.gethostbyname( host )
except socket.gaierror:
#could not resolve
print ('Hostname could not be resolved. Exiting')
sys.exit()
#Connect to remote server
s.connect((remote_ip , port))
print ('Socket Connected to ' + host + ' on ip ' + remote_ip)
#Send some data to remote server
message = "GET / HTTP/1.0\r\n\r\n"
try :
#Set the whole string
s.sendall(message.encode())
except socket.error:
#Send failed
print ('Send failed')
sys.exit()
print ('Message send successfully')
#Now receive data
messageParts = []
remaining = 4096
chunk = s.recv(remaining)
messageParts.append(chunk)
while (len(chunk) > 0):
chunk = s.recv(remaining)
messageParts.append(chunk.decode())
finalMessage = b"".join(messageParts)
print('Printing the html contents ...')
print(finalMessage)
Upon running the above code, with python version 3.2, i get the below error:
Socket Created
Socket Connected to www.google.com on ip 74.125.201.147
Message send successfully
Traceback (most recent call last):
File "TestMainServerV2.py", line 73, in <module>
finalMessage = b"".join(messageParts)
TypeError: sequence item 1: expected bytes, str found
Could anybody let me know what is the issue?
Thanks!
messageParts.append(chunk.decode())
is appending strs to messageParts.
chunk = s.recv(remaining)
messageParts.append(chunk)
is appending bytes to messageParts. (Everything that comes through a socket is bytes so chunk is a bytes object.)
Especially in Python3, one should never mix strs and bytes.
b"".join(messageParts)
raises a TypeError since b"".join expects only bytes.
You can avoid the problem by not decoding chunk. Use
messageParts.append(chunk)
instead of
messageParts.append(chunk.decode())