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Connecting two server in socket

I am a newbie in socket programming but i have a trouble that i have two server started on my localhost on port 3500 and 5000.Now i want thatmy client fist connect to the port 3500 perform some operation and then disconnect from 3500 while server will be running only client wil disconnect from 3500 and the it will connect to port 5000 and agian perform some operations.
I am using the below code to do this but getting error:-
import socket
s=socket.socket()
s.connect(('127.0.0.1',3500))
print("connectd to 3500")
print("hello friends")
s.close()
print("disconnect from 3500")
s.connect(('127.0.0.1',5000))
print("connected to 5000")
s.close()
But it is not able to connect to the second connection i.e port 5000.It gets connected to port 3500 successfully but while connecting to 5000 it throws an error.
Please any one to short out my mistake
Error:-
File "C:\Users\Lal rishav\Desktop\HubPort\test.py", line 9, in <module>
s.connect(('127.0.0.1',5000))
File "C:\Python27\lib\socket.py", line 228, in meth
return getattr(self._sock,name)(*args)
File "C:\Python27\lib\socket.py", line 174, in _dummy
raise error(EBADF, 'Bad file descriptor')

You cannot do any operations on a closed socket, create a new one instead.
s.close()
# the socket is closed, you can't use it anymore!
# get another one:
s2 = socket.socket()
s2.connect(('127.0.0.1',5000))
s2.close()
# now s2 is closed, you can't use it anymore!

How to close socket after python fail?

First, I encountered sockets in Python and faced this problem: when some error in my python code occurs, for example some syntax error before conn.close() on the second script start port is in use. The script already finished, but the socket is still open, kind of like busy socket.
Here is an error just for example:
web#web-X501A1 /var/www $ cd /home/web/www/public/py
web#web-X501A1 ~/www/public/py $ python sockets.py
connected: ('127.0.0.1', 47168)
Traceback (most recent call last):
File "sockets.py", line 164, in <module>
data = re.find('(<onvif>.*<\/onvif>)')
AttributeError: 'module' object has no attribute 'find'
web#web-X501A1 ~/www/public/py $ python sockets.py
Traceback (most recent call last):
File "sockets.py", line 154, in <module>
sock.bind(('', 9090))
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 98] Address already in use
web#web-X501A1 ~/www/public/py $ python sockets.py
Traceback (most recent call last):
File "sockets.py", line 154, in <module>
sock.bind(('', 9090))
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 98] Address already in use
Code:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(('', 9090))
sock.listen(1)
conn, addr = sock.accept()
try:
print 'connected:', addr
buffer = ''
while True:
buffer += conn.recv(1024)
data = re.find('(<code>.*<\/code>)', buffer)
print data
exit();
if not data:
continue
conn.send(data.upper())
except Exception:
pass
finally:
conn.close()

Enclose the usage of the socket in a try/finally clause. Close the socket in the finally part. Perhaps handle the exception in an except part. Something similar to this:
try:
result = x / y
except ZeroDivisionError:
print "division by zero!"
else:
print "result is", result
finally:
print "executing finally clause"

The problem here is the dirty socket closing which occurs when the script crashes without the proper TCP connection shutdown sequence. Thankfully there's a simple solution which tells the kernel to ignore the fact the socket is already in use (the port it's bound to):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
That's all, add that before the bind call and you're set. Debugging your other errors will be much simpler and less time consuming once that's done ;) See more in the docs https://docs.python.org/2/library/socket.html#socket.socket.setsockopt

If you use netstat -nutap you should notice that you connection seems like it's still up, on a state named TIME_WAIT.
That's part of TCP protocol, and according to wikipedia:
represents waiting for enough time to pass to be sure the remote TCP
received the acknowledgment of its connection termination request.
[According to RFC 793 a connection can stay in TIME-WAIT for a maximum
of four minutes known as a MSL (maximum segment lifetime).]
So, when you try to reconnect immediately to the same port, python complains that this port is still busy and cant be bound yet, saying:
socket.error: [Errno 98] Address already in use
See this old question, where it is asked how to avoid this waiting time.

Why is this MQTT client example failing?

I am trying out MQTT for the first time using Python and the mosquitto library. My client program is below. I'm trying to use the public demo MQTT server at http://www.mqtt-dashboard.com/subscribe. However the client code is failing, see error below. Any ideas on what's going on?
#!/usr/bin/env python
import mosquitto
client = mosquitto.Mosquitto("fredtest", clean_session=True)
client.connect("broker.mqttdashboard.com", 1883)
client.publish("fred.test", "hello world", 1)
client.loop_forever()
Error message:
C:\tmp>python mqttclient.py
Traceback (most recent call last):
File "mqttclient.py", line 6, in
client.connect("broker.mqttdashboard.com", 1883)
File "build\bdist.win-amd64\egg\mosquitto.py", line 582, in connect
File "build\bdist.win-amd64\egg\mosquitto.py", line 657, in reconnect
File "c:\python27\lib\socket.py", line 571, in create_connection
raise err
socket.error: [Errno 10060] A connection attempt failed because the connected pa
rty did not properly respond after a period of time, or established connection f
ailed because connected host has failed to respond

I'm not currently able to connect any client to broker.mqttdashboard.com:1883 - so this probably isn't an issue with your code.
To sanity check, have you tried connected to another broker, such as iot.eclipse.org:1883 ?

Python : file transfer giving errors

I am trying to send a file from a server to client but get errors. Please let me know where I am doing wrong.
This is my server code:
if msg in data.keys():
print("Requested file exists", msg)
f=open(msg,"rb")
datam= f.read(1024)
while (datam):
if(s.send(datam)):
print "sending data"
datam = f.read(1024)
s.close()
f.close
else:
print("File Not found",msg)
print("File Not found",data.keys())
c.close() # Close the connection
where msg contains the path address where file exists
c=client socket s=server socket
I want to read that file and send it to client but I get this error
Got connection from ('127.0.0.1', 42330)
('Requested file exists', '/home/beenish/Pictures/pew.txt')
Traceback (most recent call last):
File "server.py", line 41, in <module>
if(s.send(datam)):
socket.error: [Errno 32] Broken pipe
On client side, I have written this code to recieve that file
s.listen(15)
f = open('\home\beenish\pictures\lol.txt', 'wb')
data = s.recv(1024)
while(data):
f.write(data)
data=s.recv(1024)
f.close()
s.close # Close the socket when done
where s is the client socket
Here I get this error
Traceback (most recent call last):
File "client.py", line 26, in <module>
s.listen(15)
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 22] Invalid argument

On the client side you have an error on this line:
s.listen(15)
And the Python docs say that the argument has a system dependant maximum, usually 5. So try finding out the maximum for your system of just use a lower value and see what happen.
The server side error could be a side effect of the client side failure.

That is the kind of error you get when you call socket.listen before calling socket.bind. Keep in mind that a server always has to follow the sequence socket(), bind(), listen() and accept() in that specific order.

Python socket error - how to repair

I have this code:
>>> import socket
>>> sck = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> sck = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> sck.connect(('loaclhost', 2525))
And I have this error:
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
sck.connect(('localhost', 2526))
socket.error: [Errno 10061] No connection could be made because
the target machine actively refused it
Please helpe me. Where can be error? How can I repair it?

try changing the connection to "localhost" instead of "loaclhost"

Your code and error don't match (spelling of localhost and port number), but the error message is due to no server listening on that port. Cut and paste the exact code and error message next time.