Android ipv4 使用组播在局域网下通讯。

本文主要功能是多台Android设备使用组播在局域网下通讯。本文为在IPv4下的。

一、获取组播地址并且joinGroup：

private InetAddress broadcastAddress;
private void initCast() {
		try {
			broadcastAddress = IpUtils.getBroadcastAddress();
			multicastSocket = new MulticastSocket(7878);
			multicastSocket.joinGroup(broadcastAddress);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

 

    public static InetAddress getBroadcastAddress()
            throws IOException {
        // 获取本地所有网络接口
        Enumeration interfaces = NetworkInterface.getNetworkInterfaces();
        while (interfaces.hasMoreElements()) {
            NetworkInterface networkInterface = interfaces.nextElement();
            if (networkInterface.isLoopback() || !networkInterface.isUp()) {
               continue;
           }
            // getInterfaceAddresses()方法返回绑定到该网络接口的所有 IP 的集合
            for (InterfaceAddress interfaceAddress : networkInterface.getInterfaceAddresses()) {

                InetAddress broadcast = interfaceAddress.getBroadcast();
                if (broadcast == null) {
                    continue;
                }
                return broadcast;
            }
        }
        return null;
    }

二、发送与接受数据。

	private void receiverData() {
		new Thread(){
			public void run(){
				try {
					byte[] data = new byte[125];
					pack = new DatagramPacket(data, data.length);
					multicastSocket.receive(pack);
					Log.i(TAG, "receiverData---"+Arrays.toString(data));//show data	
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}.start();
	}

	private void sendData() {
		new Thread(){
			public void run(){
				try {
					byte[] data = "来了，老弟！".getBytes();
					DatagramPacket pack = new DatagramPacket(data, data.length, broadcastAddress,7878);
					multicastSocket.send(pack);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}.start();
		
	}

三、以上代码在多台Android设备连接同一WiFi下可行，但是有些手机可以开热点的同时连接WiFi（比如一些小米手机），这个时候可能就会出现问题。解决办法：发现同时开热点连接WiFi会有两个组播地址、两个IP地址；只需要加入组的时候将两个组播地址都加入组，并且发送数据的时候两个组都发送。看代码：

	private List listAddress;
	private void initCastT() {
		try {
			listAddress = IpUtils.getListBroadcastAddress();
			multicastSocket = new MulticastSocket(7878);
			try {//此处单独try是应为这里会抛异常，防止导致下面代码运行不到。
				multicastSocket.joinGroup(listAddress.get(0));
			} catch (Exception e) {
				// TODO: handle exception
			}
			if (listAddress.size() == 2) {
				try {
					multicastSocket.joinGroup(listAddress.get(1));
				} catch (Exception e) {
					// TODO: handle exception
				}
			}
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	private void sendDataT() {
		new Thread(){
			public void run(){
				try {
					byte[] data = "来了，老弟！".getBytes();
					DatagramPacket pack = new DatagramPacket(data, data.length, listAddress.get(0),7878);
					multicastSocket.send(pack);
					if (listAddress.size() == 2) {
						DatagramPacket pack1 = new DatagramPacket(data, data.length, listAddress.get(1),7878);
						multicastSocket.send(pack);
					}
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}.start();
	}

    public static List getListBroadcastAddress()throws IOException {
        // 获取本地所有网络接口
        List addList = new ArrayList();
        Enumeration interfaces = NetworkInterface.getNetworkInterfaces();
        while (interfaces.hasMoreElements()) {
            NetworkInterface networkInterface = interfaces.nextElement();
            if (networkInterface.isLoopback() || !networkInterface.isUp()) {
                continue;
            }
            // getInterfaceAddresses()方法返回绑定到该网络接口的所有 IP 的集合
            for (InterfaceAddress interfaceAddress : networkInterface.getInterfaceAddresses()) {

                InetAddress broadcast = interfaceAddress.getBroadcast();
                if (broadcast == null) {
                    continue;
                }
                addList.add(broadcast);
            }
        }
        return addList;
    }

	private void receiverData() {
		new Thread(){
			public void run(){
				try {
					while(true){
						byte[] data = new byte[125];
						pack = new DatagramPacket(data, data.length);
						multicastSocket.receive(pack);
						Log.i(TAG, "receiverData---"+Arrays.toString(data));//  show receiver data
					}
						
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}.start();
	}

 

最后，代码仅供大家参考，如有错误请帮忙指出，谢谢！