Networking :: Detecting Broken Connection Before Sending Data With Sockets?

I am writing a code in Python where a socket client changes data with the server. That works nice if the connection is up. However it is also supposed to work offline. So I need to be able to detect if the connection is up before sending data, but I was not able to do so. A summary of the code is like that:

Code:
try:
socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
socket.connect( (self.host, self.port) )
connected = True
except:
connected = False

if connected:
data = "some data byte"
try:
socket.send(data)
except:
connected=False
socket.close()

If I unplug the cable after the connection is ready then the socket sends data and does not detect the connection failure. What is amazing is that the client detects the connection failure just after the cable has been plugged again. Of course there is a loop in the code above and always that connected==False a new connection is made. How could the program detect the connection failure before sending data and then lead the code to an exception?