Implementing comet long polling...

[shaun5]

Are the methods included the md5 library you provided to compute the 'string hashed by SHA1' and then 'base64 encoded'? If so, what are they (I can't find the API anywhere)? This would allow me to get protocol 6 working which covers Chrome, IE9+, and Firefox. Safari and Mobile Safari use protocol 0 and that is what I have working...

What is going to be the best way to package this? Right now, I just have three scripting actions in a folder in my GML: server (fires on fileloaded and scriptenable),broadcaster (server started),closer(fires on fileclose). I was thinking one file with all the code and just have script actions to call functions. Or is there a better way?

[Ron]

md5 doesn't do sha1/base64. I'll see if I can put together something cleaner for more permanent use.

[shaun5]

Ron, I need to store a json string or two per client and have gotten stuck. How do I reference the p1 object name within the p1:callback function? I had envisioned something like WSclients[p1]['data1'] = cp1, but not sure if that will work if I had the object name... Attached is a .zip with websocket.GML, client.html, and the referenced jQuery file so you can see the basic functionality in Safari. You'll have to change the IP within the client.html file to your Girder IP. 'Onload' websocket.GML setups up the websocket server using port 8080. The 'basic send' script action will broadcast a message to all the connected clients.

Anyone wanting to give this a try will need the bit.dll file Ron posted on page 2 dropped into the Girder5 directory...

[Ron]

function dehex(str) 
    str = string.gsub(str,'[^%a-zA-Z0-9]','')
    return (string.gsub(str, '..', function (cc) return string.char(tonumber(cc, 16)) end)) 
end
function fixkey(str)
    local num = ""
    string.gsub(str,'%d', function(d) num = num .. d end)
    local _,n = string.gsub(str, ' ', ' ')
    local i = tonumber(num)/n
    return string.char(math.mod(i/256^3,256), math.mod(i/256^2,256), math.mod(i/256,256),math.mod(i,256))
end
function websocketresponse(key1, key2, end8)
    require('bit')
    local cat = fixkey(key1) .. fixkey(key2) .. end8
    local md5 = bit.newMD5()
    md5:update(cat)
    return dehex(md5:final())
end

function WScallback(p1,p2)
    if ( p2 == transport.constants.event.CONNECTIONCLOSED ) then
        print("WEBSOCKET Connection Closed by Girder")
        return
    end
    if ( p2 == transport.constants.event.NEWCONNECTION ) then
        print("WEBSOCKET New Connection")
        WSclients[p1]=true
        --actually need two different terminators \r\n for header and string.char(255) once the websocket is open...
        p1:Callback(transport.constants.parser.TERMINATED,string.char(255), 2000, function (cp1,cp2)
            if ( cp2 == transport.constants.event.CONNECTIONCLOSED ) then
                print("WEBSOCKET Connection Closed by client (can be the response to Girder sending closing message)")
                p1:Close()
                WSclients[p1]=nil
            elseif (cp2 == transport.constants.event.INCOMPLETERESPONSETIMEOUT) then
                local connecting = string.Split(string.gsub(cp1,'\r',''),"\n")
                local response = 'HTTP/1.1 101 WebSocket Protocol Handshake\r\n'
                response = response .. 'Upgrade: WebSocket\r\n'
                response = response .. 'Connection: Upgrade\r\n'
                --response = response .. 'Sec-WebSocket-Protocol: chat\r\n'
                for i in connecting do
                    if(string.sub(connecting[i],1,6) == 'Host: ') then
                        response = response .. 'Sec-WebSocket-Location: ws://'..string.sub(connecting[i],7)..'/\r\n'
                    elseif(string.sub(connecting[i],1,8) == 'Origin: ') then
                        response = response .. 'Sec-WebSocket-'..connecting[i]..'\r\n'
                    elseif (string.find(connecting[i],'Key1') ~= nil) then
                        websocket_key1 = string.sub(connecting[i],string.find(connecting[i],':',1)+2)
                    elseif (string.find(connecting[i],'Key2') ~= nil) then
                        websocket_key2 = string.sub(connecting[i],string.find(connecting[i],':',1)+2)
                    elseif (string.len(connecting[i]) == 8) then
                        ending8 = connecting[i]
                    end
                end
                p1:Write(response)
                p1:Write('\r\n')
                p1:Write(websocketresponse(websocket_key1, websocket_key2, ending8))
                print('WEBSOCKET Client Connected.')
            elseif (cp2 == transport.constants.event.RXCHAR) then
                --need to save a client's string
                print('WEBSOCKET Client Sent: ' .. string.sub(cp1,2))
            end
        end)
        return
    end
end
if ( WSclients ) then
    for c,v in pairs(WSclients) do
        c:Close()
    end
end
if ( WSt ) then
    WSt:Close()
    win.Sleep(1000)
end
WSclients = {}        
WSt = transport.New(transport.constants.transport.GIPLISTEN)
if not WSt:Open(nil, 8080) then
    print("Could not create WEBSOCKET Server.")
    WSt:Close();
    WSt = nil;
end
WSt:Callback(transport.constants.parser.TERMINATED, '\r\n', 2000, WScallback)
print("Starting WEBSOCKET Server...")
--gir.TriggerEvent("WS_broadcast", "100", 0)

In this code? Looks like you are already doing that reference?

[shaun5]

Your right. I think I tried to nest additional tables without first defining WSclients[p1]={}. I'll rewrite it and let you know.

Did you try the demo?

[Ron]

I'm sorry I didn't try yet. It's crazy how little time there is in a day.

[shaun5]

No problem! The correction worked. I now have an additional function (working in its own thread) that loops every 250ms to send differential json data updates (just like the cometreqjson) to open clients. The data monitored is defined individually by each client. Clients without websockets degrade to Ajax automatically.

If the same data is requested to be monitored by multiple clients, Girder still copies and monitors the data per client (so this could be improved if you had 4+ clients - it would just require a common data pool that is updated as clients open and close connections). The solution presented is probably best case for up to 3 or 4 simultaneous clients. Any more and the overhead of the pool will become negligible compared to the individual data copy comparisons.

I have a client side update cache to write then I will present the complete solution. The update cache will allow the client to ignore ignore updates while the client fiddles with the interface. This is nessessary to accomodate latency between everything involved in the chain (client, network, Girder, equipment)

[shaun5]

Everything is done (excluding the additional browser support - still need the Lua library) and running. I'm still on the fence on adding a common data pool (I'll add it with if there is any interest). If someone is interested in using websockets, let me know and I'll upload everything and write it up.

[Ron]

That's very cool. Which functionality do you need again? Just SHA-1 and Base64?

[shaun5]

Ron, that is correct.