xpaintro(n)

📦 version 2.1.20, in fedora 43, fedora 44

💖 XPAIntro: Introduction to the XPA Messaging System 💖

okay bestie, buckle up, because this is the intro page for the XPA Messaging System — the manual is xpaintro(n) and it lives under the SAORD Documentation umbrella, and honestly? it's giving foundational. ✨

🌸 SYNOPSIS 🌸

a little snack-sized intro to the XPA messaging system, which serves up seamless communication between all kinds of Unix event-driven programs, including X programs, Tcl/Tk programs, and Perl programs. periodt. 💅

✨ DESCRIPTION ✨

so the XPA messaging system literally makes seamless communication happen between every kind of Unix program you can think of — X programs, Tcl/Tk programs, Perl programs, the whole friend group. 🫶

and it's not just a programmer thing either, because it also gives users an easy way to talk to these XPA-enabled programs by running XPA client commands straight in the shell, or by dropping those same commands into scripts. no cap. because XPA works both at the programming level and the shell level, it's a genuinely powerful tool for unifying any analysis environment: users and programmers get maximum flexibility in choosing the best level (or levels, we love options) to access XPA services, and client access can be extended or modified easily at any time. iconic behavior honestly. 🎀

🦋 how does a program become a server tho

a program becomes an XPA-enabled server by defining named points of public access — little doorways through which data and commands can be exchanged with other client programs (and with users too, hey bestie). using standard TCP sockets as the transport mechanism, XPA supports both single-point and broadcast messaging to and from these servers. it supports direct communication between clients and servers, or indirect communication via an intermediate message bus emulation program. host-based access control is implemented, as is the ability to communicate with XPA servers across a network. the range?? unmatched. 🌈

💜 the layered interface

XPA implements a layered interface that's designed to be useful to software developers and to users. the interface is made of:

  • a library of XPA client and server routines for use in programs, and
  • a suite of high-level user programs built on top of those libraries.

using the XPA library, access points can be added to Tcl/Tk programs, Xt programs, or to Unix programs that use the XPA event loop — or any event loop based on select(). client access subroutines can be added to any Tcl/Tk or Unix program. and client access is also supported at the command line via a suite of high-level programs. multitasking queen. 👑

🌟 the major components of the XPA layered interface

  • A set of XPA server routines</b>, centered on XPANew(), which are used by XPA server programs to tag public access points with string identifiers and to register send and receive callbacks for these access points.
  • A set of XPA client routines, centered on the XPASet() and XPAGet(), which are used by external client applications to exchange data and commands with an XPA server.
  • High-level programs, centered on xpaset and xpaget, which allow data and information to be exchanged with XPA server programs from the command line and from scripts. these programs have the command syntax:
[data] | xpaset  [qualifiers ...]
         xpaget  [qualifiers ...]
  • An XPA name server program, xpans, through which XPA access point names are registered by servers and distributed to clients.

🍓 defining an XPA access point is easy, fr fr

a server application calls XPANew(), XPACmdNew(), or the experimental XPAInfoNew() routine to create a named public access point. (yes, XPAInfoNew() is experimental — we said what we said. 🙈)

an XPA service can specify "send" and "receive" callback procedures (or an "info" procedure in the case of XPAInfoNew()) to be executed by the program when an external process either sends data or commands to this access point, or requests data or information from this access point. either of the callbacks can be omitted, so a particular access point can be specified as read-only, read-write, or write-only. application-specific client data can be associated with these callbacks. having defined one or more public access points this way, an XPA server program enters its usual event loop (or uses the standard XPA event loop). slay. ✨

💅 how clients talk back

clients communicate with these XPA public access points using programs such as xpaget, xpaset, and xpainfo (at the command line), or routines such as XPAGet(), XPASet(), and XPAInfo() within a program.

both methods require specification of the name of the access point. the xpaget program returns data or other information from an XPA server to its standard output, while the xpaset program sends data or commands from its standard input to an XPA application. the corresponding API routines set/get data to/from memory, returning error messages and other info as needed. and if a template is used to specify the access point name (e.g., "ds9*"), then communication will take place with all servers matching that template. the way that just works?? obsessed. 🔥

⚠️ bestie please note: XPA currently is not thread-safe. all XPA calls must be in the same thread. no exceptions, we're not kidding, do not test this. 😭

👑 SEE ALSO 👑

see xpa(n) for a list of XPA help pages

and that's the whole vibe check, babe 💖 this was version 2.1.15, dated July 23, 2013, from the xpaintro(n) page — go forth and message your servers, you main character. 🦋🎀💜

📦 where this page comes from