XPC Between two cocoa applications in workspace, the NSXPCConnection is immediately being invalidated

I have two Cocoa Applications, one is going to be the sender and another the receiver in this XPC relationship.

In the applicationDidFinishLaunching in the sender, I first open the second receiver application

  NSError* error = nil;
  NSURL* url = [[NSBundle mainBundle] bundleURL];
  url = [url URLByAppendingPathComponent:@"Contents" isDirectory:YES];
  url = [url URLByAppendingPathComponent:@"MacOS" isDirectory:YES];
  url = [url URLByAppendingPathComponent:@"TestXPCHelper.app" isDirectory:YES];

  [[NSWorkspace sharedWorkspace] launchApplicationAtURL:url
                                                options:NSWorkspaceLaunchWithoutActivation
                                          configuration:[NSDictionary dictionary]
                                                  error:&error];

  if ( error )
  {
     NSLog(@"launchApplicationAtURL:%@ error = %@", url, error);
     [[NSAlert alertWithError:error] runModal];
  }

Then I create my NSXPCConnection

  assert([NSThread isMainThread]);
  if (self.testConnection == nil) {
     self.testConnection = [[NSXPCConnection alloc] initWithMachServiceName:NEVER_TRANSLATE(@"com.TechSmith.TestXPCHelper") options:NSXPCConnectionPrivileged];
     self.testConnection.remoteObjectInterface = [NSXPCInterface interfaceWithProtocol:@protocol(TestXPCProtocol)];

     self.testConnection.interruptionHandler = ^{
        NSLog(@"Connection Terminated");
     };

     self.testConnection.invalidationHandler = ^{

        self.testConnection.invalidationHandler = nil;
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
           self.testConnection = nil;
        }];
     };

     [self.testConnection resume];
  }

Then I try to send a message over the connection (the connection is already invalidated by here)

  id<TestXPCProtocol> testRemoteObject= [self.testConnection remoteObjectProxy];
  [testRemoteObject testXPCMethod2];

  [[self.testConnection remoteObjectProxyWithErrorHandler:^(NSError * proxyError){
     NSLog(@"%@", proxyError);
  }] testXPCMethod:^(NSString* reply) {
     NSLog(@"%@", reply);
  }];

And here is the app delegate for my receiver application:

@interface AppDelegate () <NSXPCListenerDelegate, TestXPCProtocol>

@property (weak) IBOutlet NSWindow *window;

@property NSXPCListener *xpcListener;

@end

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
   // Insert code here to initialize your application
   NSLog(@"TESTING123");

   self.xpcListener = [[NSXPCListener alloc] initWithMachServiceName:@"com.TechSmith.TestXPCHelper"];
   self.xpcListener.delegate = self;
   [self.xpcListener resume];
}

- (void)applicationDidBecomeActive:(NSNotification *)notification {
   NSLog(@"ACTIVE234");
}


- (void)applicationWillTerminate:(NSNotification *)aNotification {
   // Insert code here to tear down your application
}

- (void)run
{
   NSLog(@"RUNNING");
   // Tell the XPC listener to start processing requests.

   [self.xpcListener resume];

   // Run the run loop forever.

   [[NSRunLoop currentRunLoop] run];
}

- (BOOL)listener:(NSXPCListener *)listener shouldAcceptNewConnection:(NSXPCConnection *)newConnection
{
   NSLog(@"LISTENING");
   assert(listener == self.xpcListener);
#pragma unused(listener)
   assert(newConnection != nil);

   newConnection.exportedInterface = [NSXPCInterface interfaceWithProtocol:@protocol(TestXPCProtocol)];
   newConnection.exportedObject = self;
   [newConnection resume];

   return YES;
}

- (void)testXPCMethod:(void(^)(NSString * version))reply
{
   NSLog(@"HEY");
   reply(@"REPLY HERE");
}

- (void)testXPCMethod2
{
   NSLog(@"TWO!");
}

Here is the proxyError when I try to send a message over the connection:

Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named com.TechSmith.TestXPCHelper was invalidated." UserInfo={NSDebugDescription=The connection to service named com.TechSmith.TestXPCHelper was invalidated.}

So I think I am doing something wrong with my instantiation of the NSXPCConnection. I can't find a good example of two applications speaking to eachother-- it's always one application and a service. Is that what my problem is? I need a service inbetween the applications talking?

Is there any way to get more information on why this connection is being invalidated? That would also help a lot

So pretty straight forward problem here, Turns out initWithMachServiceName is explicitly looking for a mach service. I was using an identifier of another application process.

If I actually use an identifier of a valid mach service, there is no issue

Note that there are two other ways to create an NSXPCConnection,

with an NSXPCEndpoint or with a XPCService identifier