需求是iOS端发送udp消息指令，中控接收端接收做出相应变化。用的GCDAsyncUdpSocket，直接pod导入或者github下载加入项目中

这里是客户端，新建一个单例模式UDPManage类，记得导入GCDAsyncUdpSocket和遵守协议

#define udpPort 6666
@interface UDPManage()<GCDAsyncUdpSocketDelegate>
@property (nonatomic, strong)GCDAsyncUdpSocket *udpSocket;

@end
static UDPManage *myUDPManage = nil;
@implementation UDPManage

+(instancetype)shareUDPManage{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        myUDPManage = [[UDPManage alloc]init];
        [myUDPManage creatClientUdpSocket];
    });
    return myUDPManage;
}

-(void)creatClientUdpSocket{
    self.udpSocket = [[GCDAsyncUdpSocket alloc]initWithDelegate:self delegateQueue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)];
    //绑定端口
    NSError *error = nil;
    [self.udpSocket bindToPort:udpPort error:&error];
    //广播
    [self.udpSocket enableBroadcast:YES error:&error];
    if (error) {
        NSLog(@"error:%@",error);
    }else{
        [self.udpSocket beginReceiving:&error];
    }
}
-(void)broadcast{
   //消息内容
    NSString *str = @"这是一个测试广播";
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    //如果向特定ip发送，这里要写明ip
    NSString *host = @"255.255.255.255";
    [self.udpSocket sendData:data toHost:host port:udpPort withTimeout:-1 tag:100];
}

//成功
-(void)udpSocket:(GCDAsyncUdpSocket *)sock didSendDataWithTag:(long)tag{
    NSLog(@"发送成功嘞");
}
//失败
-(void)udpSocket:(GCDAsyncUdpSocket *)sock didNotSendDataWithTag:(long)tag dueToError:(NSError *)error{
    NSLog(@"发送失败嘞，错误信息是：%@",error);
}

调用就直接

  [[UDPManage shareUDPManage]broadcast];

服务端接收写了个简单的测试Demo

- (void)viewDidLoad {
    [super viewDidLoad];
    dispatch_queue_t dQueue = dispatch_queue_create("", NULL);
    self.receiveSocket = [[GCDAsyncUdpSocket alloc]initWithDelegate:self delegateQueue:dQueue];
    NSError *error;
 //记得绑定端口，和客户端对应的
    [self.receiveSocket bindToPort:severPort error:&error];
   
    if (error) {
        NSLog(@"服务器绑定失败");
    }
    [self.receiveSocket beginReceiving:nil];
}
//接收到消息后的协议方法
-(void)udpSocket:(GCDAsyncUdpSocket *)sock didReceiveData:(NSData *)data fromAddress:(NSData *)address withFilterContext:(id)filterContext{
    NSString *ip = [GCDAsyncUdpSocket hostFromAddress:address];
    uint16_t port = [GCDAsyncUdpSocket portFromAddress:address];
    NSString *str = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"我收到了ip：%@，port：%hu，内容是：%@ 的消息",ip,port,str);

//写了个弹框展示收到的消息
 UIAlertController* alert = [UIAlertController alertControllerWithTitle:[NSString stringWithFormat:@"ip:%@, port:%hu",ip,port]
                                                                   message:[NSString stringWithFormat:@"内容是:%@",str]
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
                                                          handler:^(UIAlertAction * action) {
                                                              //响应事件
                                                              NSLog(@"action = %@", action);
                                                          }];
    UIAlertAction* cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleDefault
                                                         handler:^(UIAlertAction * action) {
                                                             //响应事件
                                                             NSLog(@"action = %@", action);
                                                         }];
    
    [alert addAction:defaultAction];
    [alert addAction:cancelAction];
    [self presentViewController:alert animated:YES completion:nil];
}