LightMessaging

LightMessaging is an inter-process communication framework by Ryan Petrich. According to its GitHub page, it is a "simple low-level replacement for CFMessagePort". It is usually used as an API to RocketBootstrap.

Why should I use this?

• Ryan Petrich.
• Everyone else is using it.

How to integrate this library with your project

Grab the headers from rpetrich/LightMessaging, and #import <LightMessaging/LightMessaging.h>. In most use cases, be sure to build your project with RocketBootstrap as a dependency (instructions here).

Server

It is recommended that this is done in somewhere better designed to act as a server, such as SpringBoard or a daemon.

Starting the Server

LMStartService("net.iphonedevwiki.some.server", CFRunLoopGetCurrent(), (CFMachPortCallBack)some_callback);

The Callback

void some_callback(CFMachPortRef port,
                   LMMessage *request,
                   CFIndex size,
                   void *info)
{
    // get the reply port
    mach_port_t replyPort = request->head.msgh_remote_port;
    // sanity check
    if(size < sizeof(LMMessage)) {
        LMSendReply(replyPort, NULL, 0);
        LMResponseBufferFree((LMResponseBuffer *)request);
        return;
    }
    
    // get the data you recieved
    void *data = LMMessageGetData(request);

    // send some data back
    const char *msg = "lol";
    LMSendReply(replyPort, msg, strlen(msg) + 1);

    // free the response buffer??
    LMResponseBufferFree((LMResponseBuffer *)request);
}

Client

This can be run anywhere that has the appropriate permissions to send/receive data on a message port.

// setup connection
LMConnection connection = {
    MACH_PORT_NULL,
    "net.iphonedevwiki.some.server"
};

//send message
LMResponseBuffer buffer;
const char *msg = "lol wtf";
SInt32 messageId = 0x1111; // this is arbitrary i think
LMConnectionSendTwoWay(connection, messageId, msg, strlen(msg) + 1, &buffer);
LMMessage *response = &(buffer.message);

// do whatever you want !!!!
const char *data = LMMessageGetData(response);

Type helpers

There are some cool helper functions for if you want to send Images / PropertyLists / etc instead of just strings. Look at the header file or other examples to see how to use them.

Examples

• libcanopenurl (client and server are in the same file)
• Lucy (client, server)

External links

• rpetrich's JailbreakCon 2016 keynote on IPC
• LightMessaging.h