How to detect when a client disconnects from a UDS (Unix Domain Socket)

Question

When a client connects to the pipe, and sends data I can receive this fine and I can keep receiving the data. Trouble comes when the client disconnects and the while loop is still active, connection.recv() doesn't block and therefore keeps looping frantically! So I need a way to detect if a client is still connected.

I have the following code:

    pipe = './pipes/uds_defzone-lrecv'

    try:
        os.unlink(pipe)
    except OSError:
        if os.path.exists(pipe):
            raise
    self.logger.debug('Created UDS pipe: ' + pipe)

    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
    sock.bind(pipe)
    sock.listen(1)

    self.logger.debug('Waiting for connection: ' + pipe)
    connection, client_address = sock.accept()
    self.logger.debug('Connection from: ' + client_address)

    while True:

        self.logger.debug('Waiting for data')
        data = connection.recv(4096)
        self.logger.debug('Received: ' + str(data))

For reference, the sender.py code:

# Create a UDS socket
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)

# Connect the socket to the port where the server is listening
pipe = './pipes/uds_defzone-lrecv'

logger.debug('connecting to: ' + pipe)

try:
    sock.connect(pipe)
except socket.error, msg:
    logger.debug(msg)
    sys.exit(1)

try:
    message = 'THIS IS A TEST'
    logger.debug('sending: ' + message)
    sock.sendall(message)
    time.sleep(2)

finally:
    logger.debug('closing socket')
    sock.close()

TIA!

UPDATE

I can slow it down with the following code I suppose, but not exactly what I want.

    while True:

        try:
            self.logger.debug('Waiting for data')
            data_present = select.select([sock], [], [], 30)
            if data_present[0]:
                data = connection.recv(4096)
                self.logger.debug('Received: ' + data)
        except select.timeout:
            pass

UPDATE 2

For reference this is the code I came up with:

        while True:

            logger.debug('Waiting for data')
            data = connection.recv(4096)
            if not data == '':
                logger.debug('Received: ' + data)
            else:
                logger.debug('Nothing received')
                break

A hack I came up with in the process... Might be usable where it is legitimate that a client might send empty data, for signalling perhaps?

        while True:

            try:
                logger.debug('Waiting for data')
                data = connection.recv(4096)
                # *** This throws an exception when client has disconnected
                x = connection.getpeername()
                logger.debug('Received: ' + data)
            except:
                logger.debug('Client disconnected')
                break

Answer 1

connection.recv() doesn't block and therefore keeps looping frantically! So I need a way to detect if a client is still connected.

If the peer disconnects recv data will return empty data ( '' ). You need to check this and exit the loop.