Gevent-Websocket Detecting closed connection

Question

I'm using gevent-websocket with bottle.py to serve log-files. How can I detect that the websocket connection is closed from the client-side?

At the moment I'm just writing until I get a broken pipe error:

return sock.send(data, flags)
error: [Errno 32] Broken pipe

But I would like to properly detect on the server if the client closed the websocket connection.

My code looks like:

from geventwebsocket.handler import WebSocketHandler
from gevent.pywsgi import WSGIServer
import gevent.monkey
gevent.monkey.patch_all()
from bottle import route, Bottle, view, request, static_file
import json
import os
import time

app = Bottle()

# Other code

@app.route('/websocket/<filename>')
def ws_logfile(filename):
    if request.environ.get('wsgi.websocket'):
        ws = request.environ['wsgi.websocket']
        try:
            filename = os.path.join(os.getcwd(), "logfiles", filename)
            logfile = file(filename)
            lines = logfile.readlines()
            for line in lines:
                ws.send(json.dumps({'output': line}))

            while True:
                line = logfile.readline()
                if line:
                    # Here detect if connection is closed 
                    # form client then break out of the while loop
                    ws.send(json.dumps({'output': line}))
                else:
                    time.sleep(1)
             ws.close()   

         except geventwebsocket.WebSocketError, ex:
             print "connection closed"
             print '%s: %s' % (ex.__class__.__name__, ex)

if __name__ == '__main__':
     http_server = WSGIServer(('127.0.0.1', 8000), app, handler_class=WebSocketHandler)
     http_server.serve_forever()

and the corresponding client javascript code:

jQuery(document).ready(function(){
      ws = $.gracefulWebSocket("ws://" + document.location.host + "/websocket" + document.location.pathname);

      ws.onmessage = function (msg) {
        var message = JSON.parse(msg.data);
        $("#log").append(message.output + "<br>" );
      };

      window.onbeforeunload = function() {
        ws.onclose = function () {console.log('unlodad')};
        ws.close()
      };
});

Any other improvements to my code or solution are welcome.

Answer 1

Try testing for if ws.socket is not None: before sending data out on the socket.