使用UDP方式与iOS端App通讯

• 首先需要安装一个TCP&UDP测试工具
• 连接类型选择UDP
• 目标IP 设置手机的IP， 端口8888 （这个端口在App端用来绑定）
• 指定端口， 是App向回发信息所需要的端口， 具体设置如下图所示

接下来为减少代码的键入， 我直接使用CocoaAsyncSocket这个三方库，作为中间媒介完成整个过程

{
      GCDAsyncUdpSocket *udpSocket; // 定义一个socket的对象 签订代理 GCDAsyncUdpSocketDelegate
}

麦 2017/7/20 17:05:40
    /*************** UDP ***********************/
    udpSocket = [[GCDAsyncUdpSocket alloc] initWithDelegate:self delegateQueue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)];
    NSError *error = nil;
    // 绑定端口
    [udpSocket bindToPort:8888 error:&error];
    // 启用广播
    [udpSocket enableBroadcast:YES error:&error];

    if (error) {
        [SVProgressHUD showErrorWithStatus:@"启用失败"];
    }else {
        NSLog(@"%@", [udpSocket localHost]);
        // 开始接收消息
        [udpSocket beginReceiving:&error];

    }
    /*************** UDP ***********************/

#pragma mark - GCDAsyncUdpSocketDelegate
- (void)udpSocket:(GCDAsyncUdpSocket *)sock didReceiveData:(NSData *)data fromAddress:(NSData *)address withFilterContext:(nullable id)filterContext {

 NSLog(@"success");
 NSString *ip = [GCDAsyncUdpSocket hostFromAddress:address];
 NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
 NSLog(@"收到响应 %@ %@", ip, s);
 [sock receiveOnce:nil];
 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
 uint16_t port = 9999;
 [self sendBackToHost:ip port:port withMessage:s];
 });
}
- (void)sendBackToHost:(NSString *)ip port:(uint16_t)port withMessage:(NSString *)s{
    // 回一个 hello summerxx too
    char *str = "hello summerxx too" ;
    NSData *data = [NSData dataWithBytes:str length:strlen(str)];
    [udpSocket sendData:data toHost:ip port:port withTimeout:0.1 tag:200];
}