java udp 局域网
两台电脑ip分别为
192.168.1.10 
192.168.1.11

192.168.1.10 为服务端执行如下代码
public class UDPServer {
  private static final int PORT = 5000;
  private DatagramSocket dataSocket;
  private DatagramPacket dataPacket;
  private byte receiveByte[];
  private String receiveStr;

  public UDPServer() {
  Init();
  }

  public void Init() {
  try {
  dataSocket = new DatagramSocket(PORT);
  receiveByte = new byte[1024];
  dataPacket = new DatagramPacket(receiveByte, receiveByte.length);
  receiveStr = "";
  int i = 0;
  while (i == 0)// 无数据，则循环

  {
  dataSocket.receive(dataPacket);
  i = dataPacket.getLength();
  // 接收数据

  if (i > 0) {
  // 指定接收到数据的长度,可使接收数据正常显示,开始时很容易忽略这一点

  receiveStr = new String(receiveByte, 0, dataPacket.getLength());
  System.out.println(receiveStr);
  i = 0;// 循环接收

  }
  }
  } catch (Exception e) {
  e.printStackTrace();
  }
  }

  public static void main(String args[]) {
  new UDPServer();
  }
}

192.168.1.11 为客户端执行如下代码
public class UDPClient {
  private static final int PORT = 5001;
  private DatagramSocket dataSocket;
  private DatagramPacket dataPacket;
  private byte sendDataByte[];
  private String sendStr;

  public UDPClient() {
  Init();
  }

  public void Init() {
  try {
  // 指定端口号，避免与其他应用程序发生冲突

  dataSocket = new DatagramSocket(PORT+1,InetAddress.getByName("192.168.1.10"));
  sendDataByte = new byte[1024];
  sendStr = "UDP方式发送数据";
  sendDataByte = sendStr.getBytes();
  dataPacket = new DatagramPacket(sendDataByte, sendDataByte.length,
  InetAddress.getByName("localhost"), PORT);
  dataSocket.send(dataPacket);
  } catch (SocketException se) {
  se.printStackTrace();
  } catch (IOException ie) {
  ie.printStackTrace();
  }
  }

  public static void main(String args[]) {
  new UDPClient();
  }
}

服务端建立成功 没报错
客户端发送udp请求失败
报错如下
java.net.BindException: Cannot assign requested address: Cannot bind
at java.net.PlainDatagramSocketImpl.bind0(Native Method)
at java.net.PlainDatagramSocketImpl.bind(Unknown Source)
at java.net.DatagramSocket.bind(Unknown Source)
at java.net.DatagramSocket.<init>(Unknown Source)
at java.net.DatagramSocket.<init>(Unknown Source)
at udptest.UDPClient.Init(UDPClient.java:21)
at udptest.UDPClient.<init>(UDPClient.java:14)
at udptest.UDPClient.main(UDPClient.java:36)

------解决方案--------------------
你请求的端口 不对，应该是服务器的那个端口。
请教：怎么知道一个字符的ASC码