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Python Socket strange IP connection from outside

A little summary, i programm a socket server in python to fetch data from my MSSQL database and send it to my Flutter App. So far so good. Now i tried to test it from outside. I set a Port Forwarding and tried to connect it. btw it works fine. I let the server run for few hours and now i get a error messenge.
See the pic, the first ip is mine but the second is not.
Someone is trying to connect to my server. How do solve this Problem
MY Python Code
from datetime import datetime
import socket
from SqlServerRequest import SqlServerRequest
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('192.168.43.126', 2222))
s.listen(5)
while True:
clientsocket, address = s.accept()
print(f"Connection from {address} has been established.")
data = clientsocket.recv(2048).decode()
print(data)
if data == "open":
o = SqlServerRequest.dataForOpenOrders()
clientsocket.sendall(bytes(o,"utf-8"))
if data == "closed":
c = SqlServerRequest.dataForClosedOrders()
clientsocket.sendall(bytes(c,"utf-8"))
clientsocket.close()

Well, you did set up port forwarding to allow anyone on the internet to connect to your machine. Someone just did, and sent something to your program that it didn't expect, and your program crashed.
That's a great lesson on making your program robust in the face of unexpected input, for instance.
Secondly, if you want your program to actually be accessible on the internet, you will probably want some sort of authentication -- for instance, a password known by your Flutter client.
Likely on top of that, you'd want some sort of transport-layer security so people can't read your data in-flight.

The crash happens because you're trying to convert to Unicode. If this is really all there is, then it's silly to convert to Unicode at all. Just leave it as a bytes string.
wwhile True:
clientsocket, address = s.accept()
print(f"Connection from {address} has been established.")
data = clientsocket.recv(2048)
print(data)
if data == b"open":
o = SqlServerRequest.dataForOpenOrders()
clientsocket.sendall(bytes(o,"utf-8"))
if data == b"closed":
c = SqlServerRequest.dataForClosedOrders()
clientsocket.sendall(bytes(c,"utf-8"))
clientsocket.close()

Terminating client connection to server using keyboard shortcut in python

I am trying to modify a server and client chat script implemented in python. One of the requirement is that the client exits when the user types CTRL-D. My question is how do I read that the user typed (ctrl-D) and implement it within this code. Should I just close the socket like c_socket.close() without any message back to the server that I am exiting?
Thanks!
# telnet program example
import socket, select, string, sys
import readline
def prompt() :
sys.stdout.write('<You> ')
sys.stdout.flush()
#main function
if __name__ == "__main__":
if(len(sys.argv) < 3) :
print 'Usage : python MClient hostname port'
sys.exit()
host = sys.argv[1]
port = int(sys.argv[2])
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2)
# connect to remote host
try :
s.connect((host, port))
except :
print 'Unable to connect'
sys.exit()
print 'Connected to remote host. Start sending messages'
prompt()
while 1:
socket_list = [sys.stdin, s]
# Get the list sockets which are readable
read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])
for sock in read_sockets:
#incoming message from remote server
if sock == s:
data = sock.recv(4096)
if not data :
print '\nDisconnected from chat server'
sys.exit()
else :
#print data
sys.stdout.write(data)
prompt()
#user entered a message
else :
msg = sys.stdin.readline()
s.send(msg)
prompt()

Last thing first - whether you need to send something to the server before closing the socket or not depends purely on your protocol. Given the simplistic nature of the presented client code, I'd guess that closing of the socket should be enough (and the server should treat unannounced disconnects anyway as one shouldn't consider network I/O as persistent).
Second, CTRL+D will cause the returned message from sys.stdin.readline() to return as empty so you can test against that, e.g.:
msg = sys.stdin.readline()
if msg:
s.send(msg)
prompt()
else:
s.close()
sys.exit()
If you really need to send something to the server (again, depends on the protocol) you can use socket's shutdown() method before calling close().
However, keep in mind that the code presented here doesn't account for pressing the CTRL+D while reading from the socket (i.e. receiving data) so if there is a particularly long data stream coming in your CTRL+D won't be registered. You can solve this by checking the user input (and writing it to buffer for later sending) during the retrieval procedure, or you can just place your receiving code in a separate thread and leave the main thread just for user input.
You can then use the atexit module to cleanly exit from your client at any time.

Cant receive data from socket

I'm making a client-server program, and there is problem with client part.
Problem is in infinite receiving data. I've tested this particular class, listed below, in a python interpreter. I've succesfuly(maybe not) connected to google, but then program stoped in function recvData() in data = self.socket.recv(1024)
class client():
def __init__(self, host, port):
self.host = host
self.port = port
self.socket = self.connect()
self.command = commands()
def connect(self):
'''
Connect to a remote host.
'''
try:
import socket
return socket.create_connection((self.host, self.port))
except socket.error:
print(":: Failed to connect to a remote port : ")
def sendCommand(self, comm):
'''
Send command to remote host
Returns server output
'''
comman = comm.encode()
# for case in switch(comman):
# if case(self.command.RETRV_FILES_LIST.encode()):
# self.socket.send(b'1')
# return self.recvData()
# if case():
# print(":: Got wrong command")
if (comman == b'1'):
self.socket.send(b'1')
return self.recvData()
def recvData(self):
'''
Receives all the data
'''
i = 0
total_data = []
while(True):
data = self.socket.recv(1024)
if not data: break
total_data.append(data)
i += 1
if i > 9:
break
return total_data
about commented part :
I thought problem in Case realization, so used just if-then statement. But it's not.

Your problem is that self.socket.recv(1024) only returns an empty string when the socket has been shut down on the server side and all data has been received. The way you coded your client, it has no idea that the full message has been received and waits for more. How you deal with the problem depends very much on the protocol used by the server.
Consider a web server. It sends a line-delimited header including a content-length parameter telling the client exactly how many bytes it should read. The client scans for newlines until the header is complete and then uses that value to do recv(exact_size) (if large, it can read chunks instead) so that the recv won't block when the last byte comes in.
Even then, there a decisions to make. The client knows how large the web page is but may want to send a partial data to the caller so it can start painting the page before all the data is received. Of course, the caller needs to know that is what happens - there is a protocol or set of rules for the API itself.
You need to define how the client knows a message is complete and what exactly it passes back to its caller. A great way to deal with the problem is to let some other protocol such as [zeromq](http://zeromq.org/ do the work for you. A simple python client / server can be implemented with xmlrpc. And there are many other ways.
You said you are implementing a client/server program then you mentioned "connected to google" and telnet... These are all very different things and a single client strategy won't work with all of them.

Retrieve all the response in socket at one time

I am writing a client-sever program based on Python socket.
The client sends a command to the server and the server responds.
But now, some client can broadcast a message to other clients, so the client can receive more than one response at the same time.
data = s.recv(1024)
the line of code above will retrieve only one response from the server.
but if I use a while loop like this
while True:
data = s.recv(1024)
if not data: break
actually, data=s.recv(1024) will block the program when there is no data left.
I don't want to block the program and want to retrieve all the responses available in the connection at one time. Can anyone find a solution? Thank you.

You can use the select module to wait until the socket is readable or until a timeout has elapsed; you can then perform other processing. For example:
while True:
# If data can be received without blocking (timeout=0), read it now
ready = select.select([s], [], [], 0)
if s in ready[0]:
data = s.recv(1024)
# Process data
else:
# No data is available, perform other tasks

You could make the socket (s) non-blocking. This way, it will retrieve all the received responses and when there is none, it will return back. Of course, with non-blocking, you will have to periodically retry.
You could make the socket (s) non-blocking using the setblocking() method:
s.setblocking(0)
The other option is to use another thread to handle the receive part. This way, your main thread can continue doing its main task and act upon the message only if it receives one.

You can use socket.setblocking or socket.settimeout:
import socket
import sys
HOST = 'www.google.com'
PORT = 80
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.setblocking(0)
s.sendall('Hello, world')
try:
data = s.recv(1024)
except:
print 'Oh noes! %s' % sys.exc_info()[0]
s.close()
socket.recv takes two parameters, the second is a set of flags. If you're on a Linux system, you can do man recv for a list of flags you can supply, and their corresponding errors.
Lastly, in general, you can't really know that the other side is done with sending you data (unless you're controlling both sides), even if you're both following a protocol. I believe the right way to go about it is to use timeouts, and quit after sending a reset (how you do this will depend upon what protocol you're using).

Python: Socket Programming: accept() and connect calls

I have been self-learning python since few months now , and finally learning Socket programming. As an text book exercise, I am supposed to design a half-duplex chat system . Below is the code. The first request and response are just fine , but everytime I try sending a second message from client, the server seems to be hanging. The program is TCP based.
I am suspecting that since ss.accept() is being called everytime a new message has to be sent, a new thread is being created but since I have made only 1 call to sc.connect() from client , may be my new connection at the server end is hanging there for infinite time.
As a trail : I called ss.accept() outside the while loop, ie making only 1 connection and listening to data over and over on while loop, the conversations works just fine
Can someone please have a look a the code and help me understand where exactly is the issue.
Since, I am learning, I have not moved to twisted yet. I want to learn all the basics first before I move to frameworks.
!bin/usr/env python
import socket, sys
HOST =''
PORT = 1060
ADDR =(HOST,PORT)
def userinput(sock):
usermessage = input('>')
sock.sendall(str(len(usermessage)))
return usermessage
def server():
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
s.bind(ADDR)
s.listen(1)
print 'the server is listening at',s.getsockname()
while True:
ss,sockname = s.accept()
#listen to determine the bytes sent by client
msglen = ss.recv(4096)
#accept the complete message
msg = ss.recv(int(msglen))
print 'client:', repr(msg)
servermsg = userinput(ss)
ss.sendall(servermsg)
print " ---------------"
ss.close()
def client():
sc = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
sc.connect(ADDR)
while True:
message = userinput(sc)
sc.sendall(message)
replylen = sc.recv(4096)
reply = sc.recv(int(replylen))
print "reply:",reply
print "----------------"
sc.close()
if sys.argv[1:] == ['server']:
server()
elif sys.argv[1:] == ['client']:
client()
else:
print >> sys.stderr,'usage:tcp_2_7.py server|client[host]'

Your trial - accepting once and then receiving multiple messages - is how you should do this. Calling accept is waiting for a new connection - you don't need to do this every time you want to send or receive a message, just as you don't want to call connect every time you want to send or receive.
Think of it this way:
When you connect to a chat server, do you connect, send a message, then disconnect immediately? No - you have a constant open connection which messages are sent through, and the connection is only closed at the end of a chat session.
From the docs on accept:
socket.accept()
Accept a connection. The socket must be bound to an
address and listening for connections. The return value is a pair
(conn, address) where conn is a new socket object usable to send and
receive data on the connection, and address is the address bound to
the socket on the other end of the connection.