UDP应用实例-优快云博客

编写简单的UDP应用

首先，编写发送UDP数据报的示例。这需要有个服务器端能接收到内容。用Java写了个简单的接收端：

public static void main(String[] args) throws IOException {
    InetSocketAddress address = new InetSocketAddress("0.0.0.0", 5555);
    DatagramSocket datagramSocket=new DatagramSocket(address);

    System.out.println("start udp server");

    byte[] buffer=new byte[1024];

    for(;;){
        DatagramPacket datagramPacket=new DatagramPacket(buffer, buffer.length);
        datagramSocket.receive(datagramPacket);
        System.out.println("receive data:"+new String(datagramPacket.getData(),0,datagramPacket.getLength()));
    }
}

下面写发送的代码：

AsyncUdpSocket *socket=[[AsyncUdpSocket alloc]initWithDelegate:self];

NSData *data=[@"Hello from iPhone" dataUsingEncoding:NSUTF8StringEncoding];
[socket sendData:data toHost:@"192.168.0.165" port:5555 withTimeout:-1 tag:1];
NSLog(@"send upd complete.");

执行后，在接收端成功输出如下内容：

下面，写个接收端的代码：

AsyncUdpSocket *socket=[[AsyncUdpSocket alloc] initWithDelegate:self];

NSError *error = nil;
[socket bindToPort:5555 error:&error];

if (error) {
    NSLog(@"error: %@",error);
}

[socket receiveWithTimeout:-1 tag:1];
NSLog(@"start udp server");

另外，至少写这个delegate方法：

- (BOOL)onUdpSocket:(AsyncUdpSocket *)sock
     didReceiveData:(NSData *)data
            withTag:(long)tag
           fromHost:(NSString *)host
               port:(UInt16)port{
    NSLog(@"received data: %@",[[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]);
    return YES;
}

发送端，还是用java写个测试代码：

public static void main(String[] args) throws IOException {
    DatagramSocket datagramSocket = new DatagramSocket();
    byte[] buffer = "Hello!".getBytes();
    DatagramPacket datagramPacket = new DatagramPacket(buffer,
            buffer.length, new InetSocketAddress("192.168.0.144", 5555));
    datagramSocket.send(datagramPacket);
}

在iPhone日志中：

2011-07-20 15:23:33.571 SocketDemos[795:707] start udp server
2011-07-20 15:23:47.395 SocketDemos[795:707] received data: Hello!

收到了数据报。

使用UDP发送和接收组播

这里主要关注的是接收，一方面是需求上要求，另一方面，碰到过Android Wifi获取组播问题，担心iOS也有类似的机制。后来测试发现没有那么麻烦（打开组播锁）。

为了测试，还是用java编写了个发送UDP广播的简单代码：

public static void main(String[] args) throws IOException {
    int port=3333;
    MulticastSocket socket=new MulticastSocket(port);
    InetAddress address=InetAddress.getByName("239.0.0.1");
    socket.joinGroup(address);
    byte[] data="Hello everyone.".getBytes();
    DatagramPacket datagramPacket=new DatagramPacket(data,data.length,address,port);
    socket.send(datagramPacket);
    System.out.println("send ok.");

编写的iOS代码：

AsyncUdpSocket *socket=[[AsyncUdpSocket alloc] initWithDelegate:self];

NSError *error = nil;
[socket bindToPort:3333 error:&error];
[socket enableBroadcast:YES error:&error];
[socket joinMulticastGroup:@"239.0.0.1" error:&error];

if (error) {
    NSLog(@"error: %@",error);
}

[socket receiveWithTimeout:-1 tag:1];
NSLog(@"start udp server");

delegate和上面接收普通UDP一模一样：

- (BOOL)onUdpSocket:(AsyncUdpSocket *)sock
     didReceiveData:(NSData *)data
            withTag:(long)tag
           fromHost:(NSString *)host
               port:(UInt16)port{
    NSLog(@"received data: %@",[[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]);
    return YES;
}

测试得到的日志：

2011-07-20 16:14:30.338 SocketDemos[860:707] start udp server
2011-07-20 16:14:42.829 SocketDemos[860:707] received data: Hello everyone.

说明是收到了。

发送组播和前面的UDP发送类似，只是多了要做join group的操作。这里就不多说了。