[erlang-questions] Is Erlang a good tool for this particular project?

Matthew Hillsborough matthew.hillsborough@REDACTED
Wed Jul 13 16:16:59 CEST 2011

Hi Joe,

Thanks for posting links to this. Surprised Joe A. did not mention it in his
post, it has him listed as an author. :)

Just from a quick glimpse, this appears to be using MochiWeb, which is
completely HTTP based. I am not entirely sure if that's the route I am
looking to go, unless I am overlooking something here. With that said, there
are probably parts of this code I can pick out and re-use in a pure TCP
socket implementation (if this is indeed purely HTTP, which I suspect it
might be).

Would love to hear I am wrong though so I do not need to reinvent the wheel.

Thank you and happy hacking -


On Wed, Jul 13, 2011 at 9:43 AM, Joseph Norton <norton@REDACTED> wrote:

> Matt -
> There is already a client and server implementation similar to your idea
> that uses JSON as the wire format over TCP/IP.  See the section "JSF" for a
> brief description:
> http://norton.github.com/ubf/ubf-user-guide.en.html#_tcp_ip
> Download and building instructions are here:
> https://github.com/norton/ubf-jsonrpc
> Hope you find it helpful.
> - Joe N.
> On Jul 13, 2011, at 9:42 PM, Matthew Hillsborough wrote:
> Hi Ale and everyone else who replied,
> That's exactly the point, I don't think HTTP is necessary at all! There is
> the overhead of sending extraneous HTTP headers over the wire. All of those
> additional bits take additional CPU time and bandwidth (on a mobile device
> with limited CPU and even more limited bandwidth!). I see absolutely no need
> for sending HTTP headers and parsing them from the response for this,
> particularly because I am not building a web browser based application. I
> have access to C/C++/Objective-C (on iOS) and Java (on Android) and these
> are perfectly capable of working with TCP sockets. A friend of mine
> suggested that I just pass messages to the server as JSON using a prefixed
> header that specifies the length of the message. That would be it! Simple
> and compact.
> I just wanted to validate the idea and see if others thing I'll run into
> too many edge cases uses TCP sockets via an RPC type server to build this
> server/client architecture out. I want to really make it reusable so all of
> my mobile products can use it.
> Loving all the advice coming in! Thanks all.
> Matthew.
> On Tue, Jul 12, 2011 at 5:03 PM, Ale <peralta.alejandro@REDACTED> wrote:
>> Hi,
>> Just a thought here... Erlang is great for scalability and handling
>> multiple connections, and well I'm sure a lot of people can give you a
>> better description fo this, but it occurred to me if you considered
>> other protocols instead of HTTP? The problem seems to be there rather
>> than the language you write your sever. It occurred to me that you
>> might benefit from using Jabber/XMPP. Googling I found some iOS jabber
>> clients http://code.google.com/p/xmppframework/ and the cannonical
>> jabber server is written in Erlang.
>> Regards,
>> 2011/7/12 Matthew Hillsborough <matthew.hillsborough@REDACTED>:
>> > Greetings Erlang community,
>> > Let me further elaborate on my question that's in the subject of this
>> > message. I tried to reach out with this question on StackOverflow,
>> however I
>> > did not have much luck there. Perhaps the community here can provide
>> some
>> > feedback here for me to let me know if I'm on the right track or if
>> Erlang
>> > is not the right tool for what I'm trying to accomplish.
>> >
>> > I'm building native mobile applications in both iOS and Android. These
>> apps
>> > require "realtime" updates from and to the server, same as many (but not
>> > all) network-based application does (Facebook, social games like Words
>> with
>> > Friends, Finance applications, etc). The communication here is
>> > bi-directional, in the sense that the server might have updates for the
>> > mobile clients and the clients will be pushing data down to the server
>> > whenever necessary.
>> >
>> > I think using HTTP long polling for this is over kill in the sense that
>> long
>> > polling can be detrimental to battery life, especially with a lot of TCP
>> > setup/teardown for every HTTP connection the device needs to send out
>> > through the wire. It might make sense to have the mobile applications
>> use
>> > persistent TCP sockets to establish a connection to the server, and send
>> RPC
>> > style commands to the server for all web service communication. This
>> > ofcourse, would require a server to handle the long-lived TCP connection
>> and
>> > be able to speak to a web service once it makes sense of the data passed
>> > down the TCP pipe. I'm thinking of passing data in plain text using JSON
>> or
>> > XML and then using some kind of Erlang interface to HTTP to call a web
>> > service to handle all the REST type communication. The responses would
>> then
>> > go back to the "RPC" Erlang instance, which would send the updates to
>> the
>> > appropriate client(s).
>> >
>> > Perhaps an Erlang based RPC server would do well for a network based
>> > application like this. It would allow for the mobile apps to send and
>> > receive data from the server all over one connection without multiple
>> > setup/tear down that individual HTTP requests would do. Since no web
>> browser
>> > is involved, we do not need to deal with the nuances of HTTP
>> long-polling at
>> > the mobile client level. I also haven't seen great long
>> polling/keep-alive
>> > support on the client-side in iOS, but that's irrelevant for the
>> community
>> > here.
>> >
>> > A lot of these "COMET" and long-polling/streaming servers are built with
>> > HTTP in mind. I'm thinking just using a plain-text protocol over TCP is
>> > better catered for the type of app I'm building, will make the client
>> more
>> > responsive, allow for receiving of updates from the server without
>> > constantly polling the server, etc.
>> >
>> > I also looked into HTTP pipelining, but it doesn't look to be worth the
>> > trouble when it comes to implementing it on the clients. Also, I'm not
>> sure
>> > if it would allow for bi-directional communication in the
>> client<->server
>> > communication channel.
>> >
>> > Am I completely out of line in thinking that building a custom solution
>> in
>> > Erlang is a good idea here? To my understanding, Erlang excels at
>> servers
>> > like this, and if I run the server on tcp/80, I should be able to avoid
>> most
>> > firewall/port issues. The client would need work to deal with timeouts,
>> re
>> > connections, acknowledging receipt of asynchronous requests, but that's
>> not
>> > Erlang's problem.
>> >
>> > Has anyone built something similar before? Should I just stick to a web
>> > server and deal with "COMET" type technologies? (WebSockets,
>> long-polling,
>> > client-side polling).
>> >
>> > Was hoping someone could solidify that I'm not entirely insane for
>> wanting a
>> > better solution than HTTP would serve in this case, at least at the
>> client
>> > level. I'll still be using HTTP/REST extensively, the Erlang server
>> would
>> > just handle the persistent connections and messaging to the Web Service
>> > (which would probably be something like Django or Rails).
>> >
>> > Sorry for the long post; I am just excited to get into the heads of
>> people
>> > who are smarter than I.
>> >
>> > Happy hacking!
>> >
>> > Matthew
>> >
>> > _______________________________________________
>> > erlang-questions mailing list
>> > erlang-questions@REDACTED
>> > http://erlang.org/mailman/listinfo/erlang-questions
>> >
>> >
>> --
>> Ale.
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> Joseph Norton
> norton@REDACTED
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