Re: Suggestions for custom application-layer protocol?

From: Gordon Burditt (gordonb.ir1o9_at_burditt.org)
Date: 05/25/05

  • Next message: Måns Rullgård: "Re: Suggestions for custom application-layer protocol?" 
    Date: Wed, 25 May 2005 18:03:17 -0000

    >I want the protocol to be text based rather than binary since the data
    >throughput is low. I also want the protocol to be based on TCP/IP. Does
    >anyone here have any suggestions on the design of a simple protocol? Are
    >there simple, standard ways of formatting text messages to be sent over a
    >TCP socket (such as comma-separated)? I would prefer to avoid the
    >complexities of XML. Since either the embedded device or the monitoring
    >terminal can initiate a message, is it preferable to have TCP servers
    >running on both sides? Or is it better to simply leave a TCP connection
    >open between client and server? Any suggestions on ultra-simple standard
    >protocols that do something similar to this?

    Take a look at protocols like SMTP, NNTP, POP3, IMAP, etc. Another
    example to look at is the "AT" command set of modems (although this
    doesn't use TCP). A command is one line of text. It starts with
    some kind of command verb that identifies what follows. The response
    is usually one line of text, and something at the beginning of the
    line identifies what kind of response it is (status code) and may
    identify whether it's the last line or not. The status codes are
    in groups so a client doesn't have to be aware of all the status
    codes (e.g. 4NN is a temporary failure of some kind, 5NN is a
    permanent failure).

    Spontaneous responses make the protocol a bit more complicated.
    You need to be able to identify a spontaneous response (status code)
    and perhaps the spontaneous response only says there IS data, and
    the client needs to ask for it to actually get it sent. IMAP
    uses tags on requests and replies so you can match them up, and
    deals with sponteneous responses.

    Use any kind of field separator that's appropriate for the data you
    are sending. POP3 and IMAP use spaces. Commas might be more
    appropriate for certain kinds of data.

    Testing is generally easy: telnet to the appropriate port and
    manually type commands. Read the responses.

                                                    Gordon L. Burditt

  • Next message: Måns Rullgård: "Re: Suggestions for custom application-layer protocol?"

    Relevant Pages

    • Re: Suggestions for custom application-layer protocol?
      ... > the embedded device, and control messages from the monitoring terminal. ... I also want the protocol to be based on TCP/IP. ... > to be sent over a TCP socket? ... field for a command or status code, and put your data in the other fields. ...
      (comp.os.linux.embedded)
    • Re: Suggestions for custom application-layer protocol?
      ... > the embedded device, and control messages from the monitoring terminal. ... I also want the protocol to be based on TCP/IP. ... > to be sent over a TCP socket? ... field for a command or status code, and put your data in the other fields. ...
      (comp.unix.programmer)
    • Re: TCP question
      ... All TCP data is transmitted as a series of bytes. ... Take the MSN protocol for example. ... The first part of the command is a Command String ... sort of data you are transmitting. ...
      (microsoft.public.dotnet.languages.vb)
    • Re: TCP question
      ... I wonder, because data is transferred as Bytes, should the headers be binary ... > All TCP data is transmitted as a series of bytes. ... > Take the MSN protocol for example. ... The first part of the command is a Command String (a ...
      (microsoft.public.dotnet.languages.vb)
    • Re: Sending alphanumeric data to pager
      ... Thank you for your response, Matthias. ... I am still trying to get hold of that protocol. ... >> I cannot test it because I am not subscribed to any pager services. ...
      (microsoft.public.win32.programmer.tapi)