# delphizmq

**Repository Path**: jason156/delphizmq

## Basic Information

- **Project Name**: delphizmq
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: LGPL-3.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-02-24
- **Last Updated**: 2024-05-11

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

0MQ Binding for Delphi
======================

This is a binding for [ZMQ](http://www.zeromq.org). Should work with Delphi7+ versions and with FPC 2.6.0. 

General
=======

The package contains a wrapper (zmq.pas), and a higher level api (zmqapi.pas). 
It should work with ZMQ 2.2.x, and with 3.2.x. For version 2.2.x undefine zmq3, in
zmq.inc. The dll's are not part of this repo, you can download the appropriate from 
[the official distro](http://www.zeromq.org/intro:get-the-software), and rename it 
to `libzmq.dll`.

This is a work in progress, please open an issue if you find bugs, or have question, 
or proposal.

Usage
=====

You should use the higher level api, which'll save you a lot of time, and incidentally 
the code'll be easier to read.

First, you need to create a context

    context := TZMQContext.Create; 
    
There are various socket types, see the [Guide](http://zguide.zeromq.org), each has a 
constant. To create for example a REP socket, just write this:

    socket := context.Socket( stRep );
    
    // binding the socket
    socket.bind( 'tcp://*:5555' );
    
    // connecting the socket
    socket.connect( 'tcp://localhost:5555' );
    
To send messages the api has several methods. You can send single, or Multipart messages,
in blocking or nonblocking (in the v3 it's called dontwait) mode.
    
    // sending a Utf8String in blocking mode(default) is just as easy as this:
    socket.send( 'Hello' );
    
    // or in non-blocking mode
    socket.send( 'Hello', [rsfNoBlock] );
    // in this case if the message cannot be queued an EZMQException is raised,
    // with a value EAGAIN.
    
    // sending data from a stream (don't forget to set the position of the stream, to read to)
    socket.send( stream, size );
    
    // sending multipart messages.
    // Utf8Strings:
    socket.send( ['Hello','World'] );
    
    //this is equivalent to:
    socket.send( 'Hello', [rsfSndMore] );
    socket.send( 'World' );
    
    // or use TStrings. TString.Strings interpreted as Utf8Strings!
    tsl := TStringList.Create;
    tsl.Add( 'Hello' );
    tsl.Add( 'World' );
    socket.send( tsl );
    tsl.Free;
      
Receiving messages is as easy as

    msize := socket.recv( msg );
    // the new message is in the msg, and msize holds the length of the message
    
    // to a Stream
    msize := socket.recv( stream );
    
    // read multipart message
    tsl := TStringList.Create;
    mcount := socket.recv( tsl );
    // this will add message parts to the stringlist, and returns
    // the count of the messages received.

**CTRL+C Handling**
  
it's a bit tricky. On windows signal handling is different, than in posix systems.
Blocking calls won't receive SIGINT, just block continously. To overcome this issue,
the installed handler terminates the contexts, so blocking calls like `recv`, `poll`,
etc... will receive `ETERM`. It's just on Windows.

if you code your infinite loops like this, you can terminate cleanly.

    while not context.Terminated do
    try
      socket.recv( msg );
    except
      // handle exception, or
      context.Terminate;
      // if CTRL+C was pressed, on windows the context already 
      // terminated
    end;
    
    context.Free;
    
**Polling**

Polling can work in two different ways, let's call the first 
_synchronous_, the second _asynchronous_ way. The _asynchronous_
version creates a thread, and do the polling there.

  - synchronous 
    
        // create context
        context := TZMQContext.Create;
        socket := context.Socket( stDealer );
        socket.connect( address );
    
        // Create the poller. The `true` parameter tells 
        // the poller to use synchronous polling
        poller := TZMQPoller.Create( true );
    
        // register the socket.
        poller.register( socket, [pePollIn] );
        
        timeout := 100; // 100ms
        while not context.Terminated do
        begin
          rc := poller.poll(timeout);
          if rc > 0 then
            do something...
        end;
        
        poller.Free;
        socket.Free;
        context.Free;
     
  - asynchronous way
    
  This implementation uses a kind of reactor pattern, the poller
  starts a new thread , and creates a pair socket connection 
  between the class and the created thread. So this poller 
  implementation is not thread safe, don't register, deregister
  sockets in different threads.
  
        procedure TMyClass.pollerEvent( socket: TZMQSocket; event: TZMQPollEvents );
          begin
            do something...
          end;
          
        // create context.
        context := TZMQContext.Create;
        
        socket := context.Socket( stDealer );
        socket.connect( address );
        
        // create the poller. the second parameter can be nil, than
        // the poller creates it's own context.
        poller := TZMQPoller.Create( false, context );
        
        poller.onEvent := pollerEvent;

        // register the socket. If the third parameter is true,
        // than the register block until the socket is registered.
        poller.register( socket, [pePollIn], false );
        
    
  
Monitoring Sockets ( just available in `v3.2.2`)

    // define a callback like this.
    procedure TMyClass.MonitorCallback( event: TZMQEvent );
    begin
      // do something.
    end;
    
    // Register the callback
    socket.RegisterMonitor( MonitorCallback, cZMQMonitorEventsAll );
    
    // The `MonitorCallback` is called from a separate thread, created by `RegisterMonitor`
    
    // you can deregister the monitoring with calling.
    socket.DeRegisterMonitor; 

**Threads**

  Similar to the czmq api. this binding also supports attached and detached thread creation. 
  There are two ways to use this class, call the `CreateDetached` or `CreateAttached` constructors,
  with parameters, or create your own descendent class and override the `DoExecute` method.
  
  - Creating a detached thread.
        
        procedure TMyClass.DetachedMeth( args: Pointer; context: TZMQContext );
        var
          socket: TZMQSocket;
        begin
          socket := context.Socket( TZMQSocketType( Args^ ) );
          Dispose( args );
        end;
        
        var
          thr: TZMQThread;
          sockettype: ^TZMQSocketType;
        begin
          New( sockettype );
          sockettype^ := stDealer;
          thr := TZMQThread.CreateDetached( DetachedMeth, sockettype );
          thr.FreeOnTerminate := true;
          thr.Resume;
        end;
        
  or
        
        // create descendant class
        TMyZMQThread = class( TZMQThread )
        protected
          procedure doExecute; override;
        end;
        
        procedure TMyZMQThread.doExecute
        var
          socket: TZMQSocket;
        begin
          // do something cool.
          socket := Context.socket( TZMQSocketType(Args^) );
        end;
        
        var
          myThread: TMyZMQThread;
          sockettype: ^TZMQSocketType;
        begin
          New( sockettype );
          sockettype^ := stDealer;
          
          // the nil context means it will be a detached thread.
          myThread := TMyZMQThread.Create( sockettype, nil );
          myThread.Resume;
        end;
        
        
  - Creating an attached thread.
        
        procedure TMyClass.AttachedMeth( args: Pointer; context: TZMQContext; pipe: TZMQSocket );
        var
          socket: TZMQSocket;
          msg: Utf8String;
        begin
          while not context.Terminated do
          begin
            // do some cool stuff.
            socket := Context.socket( TZMQSocketType(Args^) );
            
            // you can use pipe to communicate.
            pipe.recv( msg );
          end;
        end;
        
        var
          thr: TZMQThread;
          sockettype: ^TZMQSocketType;
        begin
          New( sockettype );
          sockettype^ := stDealer;
          thr := TZMQThread.CreateAttached( AttachedMeth, context, sockettype );
          thr.FreeOnTerminate := true;
          thr.Resume;

          
          // use thr.pipe to send stuff to the thread.
          thr.pipe.send( 'hello thread' );
        end;
        
  or
        
        // create descendant class
        TMyZMQThread = class( TZMQThread )
        protected
          procedure doExecute; override;
        end;
        
        procedure TMyZMQThread.doExecute
        var
          socket: TZMQSocket;
          msg: Utf8String;
        begin
          // do something cool.
          socket := Context.socket( TZMQSocketType(Args^) );
          while true do
          begin
            pipe.recv( msg );
          end;
        end;
        
        var
          myThread: TMyZMQThread;
          sockettype: ^TZMQSocketType;
        begin
          New( sockettype );
          sockettype^ := stDealer;

          myThread := TMyZMQThread.Create( sockettype, context )
          myThread.Resume;
          
          myThread.pipe.send( 'Hello thread' );
        end;

Examples
========

examples are in the [zguide](https://github.com/bvarga/zguide) `examples/Delphi` folder.

Changes
=======
* TZMQThread class
* Fixed bug in context.Destroy
* New poller class
* poll function of TZMQPoller has a new optional parameter "pollCount".
* Upgrade dll-s to v3.2.2 RC2
* New monitoring logic implemented.
* Default ZMQ version for the binding is now 3.2 ( can switch back to 2.2 by not defining `zmq3` in the `zmq.inc` file )

Authors
=======

The following people have contributed to the project:

    Balazs Varga <bb.varga@gmail.com> 
    Stathis Gkotsis <stathis.gkotsis@gmail.com>
    Stephane Carre <scarre.lu@gmail.com>

Copying
=======

Free use of this software is granted under the terms of the GNU Lesser General
Public License (LGPL). For details see the files `COPYING.LESSER` included with 
the distribution.