Category on NSSocketPort to create ports bound only to `localhost`, and thus only accessible to other processes on the same Mac.

NSSocketPort+initWithLocalhostTCPPort.h

//
//  NSSocketPort+initWithLocalhostTCPPort.h
//  Typesetter
//
//  Created by Brent Royal-Gordon on 4/10/13.
//  Copyright (c) 2013 Groundbreaking Software. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSSocketPort (initWithLocalhostTCPPort)

- (instancetype)initWithLocalhostTCPPort:(unsigned short)port;

@end

NSSocketPort+initWithLocalhostTCPPort.m

//
//  NSSocketPort+initWithLocalhostTCPPort_.m
//  Typesetter
//
//  Created by Brent Royal-Gordon on 4/10/13.
//  Copyright (c) 2013 Groundbreaking Software. All rights reserved.
//

#import "NSSocketPort+initWithLocalhostTCPPort.h"
#import <sys/socket.h>
#import <netinet/in.h>

@implementation NSSocketPort (initWithLocalhostTCPPort)

- (instancetype)initWithLocalhostTCPPort:(unsigned short)port {
    NSMutableData * addr = [NSMutableData dataWithLength:sizeof(struct sockaddr_in)];
    
    struct sockaddr_in * localhost = addr.mutableBytes;
    localhost->sin_len = sizeof(struct sockaddr_in);
    localhost->sin_family = PF_INET;
    localhost->sin_port = htons(port);
    localhost->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    
    return [self initWithProtocolFamily:PF_INET socketType:SOCK_STREAM protocol:IPPROTO_TCP address:addr];
}

@end