Adding client_server NSNotification example

X. NU/custom/mach_ipc/client_server_NSNotification/Makefile

@@ -0,0 +1,15 @@
+CC = clang
+CFLAGS = -framework Foundation
+
+all: client server
+
+client: client.m
+	$(CC) $(CFLAGS) client.m -o client
+
+server: server.m
+	$(CC) $(CFLAGS) server.m -o server
+
+clean:
+	rm -f client server *.o
+
+.PHONY: all clean

X. NU/custom/mach_ipc/client_server_NSNotification/client.m

@@ -0,0 +1,19 @@
+// client.m
+#import <Foundation/Foundation.h>
+
+int main(int argc, char *argv[]) {
+    @autoreleasepool {
+        if (argc != 2) {
+            NSLog(@"Usage: %s <message>", argv[0]);
+            return 1;
+        }
+        
+        NSString *message = [NSString stringWithUTF8String:argv[1]];
+        [[NSDistributedNotificationCenter defaultCenter]
+            postNotificationName:@"com.crimson.message_service"
+            object:nil
+            userInfo:@{@"message": message}
+            deliverImmediately:YES];
+    }
+    return 0;
+}

X. NU/custom/mach_ipc/client_server_NSNotification/server.m

@@ -0,0 +1,31 @@
+// server.m
+#import <Foundation/Foundation.h>
+
+@interface MessageServer : NSObject
+- (void)handleMessage:(NSNotification *)notification;
+@end
+
+@implementation MessageServer
+- (id)init {
+    if (self = [super init]) {
+        [[NSDistributedNotificationCenter defaultCenter] 
+            addObserver:self
+            selector:@selector(handleMessage:)
+            name:@"com.crimson.message_service"
+            object:nil];
+    }
+    return self;
+}
+
+- (void)handleMessage:(NSNotification *)notification {
+    NSLog(@"Received: %@", notification.userInfo[@"message"]);
+}
+@end
+
+int main() {
+    @autoreleasepool {
+        MessageServer *server = [[MessageServer alloc] init];
+        [[NSRunLoop currentRunLoop] run];
+    }
+    return 0;
+}