SimpleIPC unit

The SimpleIPC unit provides classes to implement a simple, one-way IPC mechanism using string messages. It provides a TSimpleIPCServer component for the server, and a TSimpleIPCClient component for the client. The components are cross-platform, and should work both on Windows and UNIX-like systems.

The Unix implementation of the SimpleIPC unit uses file-based sockets. It will attempt to clean up any registered server socket files that were not removed cleanly.

It does this in the unit finalization code. It does not install a signal handler by itself, that is the task of the programmer. But program crashes (access violations and such) that are handled by the RTL will be handled gracefully.

This also means that if the process is killed with the KILL signal, it has no chance of removing the files (KILL signals cannot be caught), in which case socket files may remain in the file system. However, the client code attempts to cater for this and will remove the stale sockets if it detects them.

Under Windows, the communication is done through WM_COPYDATA messages. Starting from Windows Vista it is forbidden to send messages between service applications and desktop applications, so a SimpleIPC client in a desktop application cannot connect to a SimpleIPC server in a service application and vice versa.

Classes and records

EIPCError	class	Error reporting exception.
TIPCClientComm	class	Internal client-side communication protocol.
TIPCServerComm	class	Internal message communication component.
TIPCServerMsg	class	Server message queue class.
TIPCServerMsgQueue	class	A simple message queue, with FIFO characteristics and overflow management.
TMsgHeader	record	Message header record.
TSimpleIPC	class	Ancestor for client/server simple IPC classes.
TSimpleIPCClient	class	Simple IPC client component.
TSimpleIPCServer	class	Simple IPC server component.

Types

TIPCClientCommClass	type	Class reference for TIPCClientComm.
TIPCMessageOverflowAction	enumeration	Action to take when the message queue is going to overflow.
TIPCServerCommClass	type	Class reference for TIPCServerComm.
TMessageQueueEvent	procedure type	Event handler, executed when a message is detected on the queue.
TMessageType	type	For backwards compatibility.

Constants

MsgVersion	constant	Current version of the messaging protocol.
mtString	constant	String message type.
mtUnknown	constant	Unknown message type.

Resource strings

SErrActive	resource string	Error message if client/server is active.
SErrInActive	resource string	Error message if client/server is not active.
SErrMessageQueueOverflow	resource string	Too many messages in the message queue.
SErrServerNotActive	resource string	Error message if server is not active.
SErrThreadContext	resource string	Thread context error message.
SErrThreadFailure	resource string	Thread failure message.

Variables

DefaultIPCClientClass	variable	Default client communication class.
DefaultIPCMessageOverflowAction	variable	Default action to take take when the message queue is going to overflow.
DefaultIPCMessageQueueLimit	variable	Default maximum queue message size.
DefaultIPCServerClass	variable	Default server communication class.

Uses

• Contnrs
• SyncObjs
• Classes
• SysUtils