TCP Socket Connection Printing Blanks - objective-c

Question

I have a label printer, a Brady i3300, that I am connecting to from my iPad using a tcp socket (using the CocoaAsyncSocket framework). Each time I send data to the printer, it prints, but the label is always blank.
Process
First, I run connectToPrinter, and the didConnectToHost delegate fires. After the successful connection, I call printLabelToPrinter, where the printer is sent the data. The didWriteDataWithTag delegate is called just after this, the printer begins / finishes printing, but the label is blank.
It has not mattered thus far what content is in the data file (explained below), so it feels like a connection issue...Regardless, the printer seems to be receiving the request without any data along with it.
Why is the printer printing blank labels?
Code & Files
Here is my connection setup:
- (void)connectToPrinter {
// Create the socket
self.socket = [GCDAsyncSocket.alloc initWithDelegate:self delegateQueue:dispatch_get_main_queue()];
// Connect to the printer via IP and port
NSError *err = nil;
if (![self.socket connectToHost:#"10.0.0.147" onPort:9100 error:&err]) {
// Something went wrong!
NSLog(#"I goofed: %#", err);
}
}
- (void)socket:(GCDAsyncSocket *)sock didConnectToHost:(NSString *)host port:(uint16_t)port {
NSLog(#"connected to host!: %#", host);
[self printLabelToPrinter];
}
Note: the .zpl file ref below contains a ZPL printing script, one of the supported languages of Brady printers
- (void)printLabelToPrinter {
// Get the ZPL file and convert it over to data
NSString *filePath = [NSBundle.mainBundle pathForResource:#"label" ofType:#".zpl"];
NSData *data = [NSFileManager.defaultManager contentsAtPath:filePath];
// Write the data to the printer
[self.socket writeData:data withTimeout:10 tag:1];
}
- (void)socket:(GCDAsyncSocket *)sock didWriteDataWithTag:(long)tag {
NSLog(#"did write data: %ld", tag);
}
Here is the .zpl file
^XA
^CF0,60
^FO50,50^GB100,100,100^FS
^FO75,75^FR^GB100,100,100^FS
^FO50,300
^FO504,300^FDTest
^XZ