pascal-nodejs-ipc

Free Pascal library for communicating with a parent Node.js process through Inter Process Communications (IPC).

Tested with FPC v3.0.4, v3.1.1, node v11.9.0 on Linux x64

Example project

Usage

parent.js

const { spawn } = require('child_process');

const proc = spawn('./dist/child', {
  stdio: ['pipe', 'pipe', 'pipe', 'ipc'],
});

// Using built-in Node.js IPC
proc.on('message', msg => console.log('parent, new message:', msg));
proc.send({ source: 'Node.js' });

child.pas

program child;

uses
  {$ifdef Unix}cthreads,{$endif} nodeipc;

type
  TApplication = class
  private
    FNodeIpc: TNodeIpcProtocol;
    procedure OnMessage(Message: Variant);
  public
    procedure Run;
  end;

procedure TApplication.OnMessage(Message: Variant);
begin
  WriteLn('child, new message: ', Message);
end;

procedure TApplication.Run;
begin
  FNodeIpc := TNodeIpcProtocol.Create;
  FNodeIpc.OnMessage := @OnMessage;
  FNodeIpc.Send('{"source":"Free Pascal"}');

  WriteLn('Press any key to exit');
  ReadLn();
end;

var
  App: TApplication;
begin
  App := TApplication.Create;
  App.Run;
end.

How Node.js built-in IPC module works

• Node.js passes a bi-directional IPC stream to a child process as a file descriptor.

const proc = spawn('./dist/child', {
  stdio: ['pipe', 'pipe', 'pipe', 'ipc'],
});

• To send a message trough this stream, each process can send JSON encoded strings separated by a new line char.

• To get the exact file descriptor, a child process reads NODE_CHANNEL_FD environment variable.