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I'm trying to learn python (using the Flask micro-framework) and I am confused because somewhere in my code i'm keeping the server open I believe.
I spin up my server with 'python app.py' and then close it however.... it still lives!
I'm not sure how this is possible but i must have done something wrong with a connection.
There are two questions here really.
First: How can I find the active connection/socket and close it
Second: Is there a way I can diagnose what is having an open connection, my hunch is that sqlLite is not closing as it is the last thing I implemented.
This is a one file application (minus a config file and static content) so I can post the code if required.
Error generated (Folder locations changed):
/Development/flask_projects/test_email/env/bin/python /Development/flask_projects/test_email/app.py * Running on http://127.0.0.1:5000/ Traceback (most recent call last): File "Development/flask_projects/test_email/app.py", line 58, in <module> app.run() File "Development/flask_projects/wtchn_email/env/lib/python2.7/site-packages/Flask-0.8-py2.7.egg/flask/app.py", line 703, in run run_simple(host, port, self, **options) File "/Library/Python/2.7/site-packages/Werkzeug-0.7.1-py2.7.egg/werkzeug/serving.py", line 612, in run_simple test_socket.bind((hostname, port)) File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.py", line 224, in meth return getattr(self._sock,name)(*args) socket.error: [Errno 48] Address already in use 
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You need to call shutdown() first and then close(), and shutdown takes an argument. I modified your close() to do this and it works.
The close() method of ServerSocket class is used to close this socket. Any thread currently blocked in accept() will throw a SocketException. The associated channel is also closed by it if it has any.
Python takes the automatic shutdown a step further, and says that when a socket is garbage collected, it will automatically do a close if it's needed.
Short answer: use a non-blocking recv(), or a blocking recv() / select() with a very short timeout. Long answer: The way to handle socket connections is to read or write as you need to, and be prepared to handle connection errors.
If you use linux you can use lsof to find out which process is using a given port, you might have to install it first though, usage is pretty simple:
lsof -i :5000 To kill the python process which is listening on port 5000 :
sudo lsof -i :5000 | grep "python" | cut -d " " -f3 | xargs kill -9
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