[英]Binding error in UDP networking
在通过UDP的我的服务器客户端程序中,我的服务器接收消息,将该消息显示到控制台并从客户端显示,然后再次发送给客户端。
这是我的服务器,它从命令行输入名称
import java.io.IOException;
import java.net.*;
class Stest implements Runnable {
private String str[];
DatagramSocket sock;
DatagramPacket pack;
String Sname;
Stest(String str[]) throws SocketException, UnsupportedEncodingException, IOException {
this.str = str;
this.Sname = str[0];
System.out.println(Sname);
new Thread(this).start();
}
public void run() {
while (true) {
byte[] data = new byte[1024];
try {
sock = new DatagramSocket(5050);
} catch (SocketException ex) {
Logger.getLogger(test.class.getName()).log(Level.SEVERE, null, ex);
}
pack = new DatagramPacket(data, data.length);
try {
sock.receive(pack);
} catch (IOException e) {
e.printStackTrace();
}
String s = null;
try {
s = new String(pack.getData(), "UTF-8");
System.out.println(s);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
DatagramPacket dp = null;
try {
dp = new DatagramPacket(s.getBytes("UTF-8"), s.getBytes("UTF-8").length);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
dp.setPort(1);
dp.setAddress(pack.getAddress());
try {
sock.send(dp);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public class test{
public static void main(String[] args) {
try {
Stest stest= new Stest(args);
} catch (IOException ex) {
Logger.getLogger(test.class
.getName()).log(Level.SEVERE, null, ex);
}
}
}
这是我的客户端,它使用其名称,侦听端口,服务器ip地址和服务器名称,并将消息发送到服务器,并再次从服务器接收该消息,并将该消息显示到控制台。
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
class UDPClient {
String username;
String listening_port;
String serverAddress;
String servername;
public UDPClient(String username, String listening_port, String serverAddress, String servername) {
this.username = username;
this.listening_port = listening_port;
this.serverAddress = serverAddress;
this.servername = servername;
}
}
class ClientListen extends UDPClient implements Runnable {
Thread t;
DatagramSocket clientlistensocket;
DatagramPacket clientlistenpacket;
byte[] data;
public ClientListen(String username, String listening_port, String serverAddress, String servername) {
super(username, listening_port, serverAddress, servername);
try {
clientlistensocket = new DatagramSocket(Integer.parseInt(listening_port));
} catch (Exception e) {
System.out.println(e + " ClientListen");
}
t = new Thread(this, "ClientListen");
t.start();
}
public void go() {
String messag = new String(clientlistenpacket.getData());
System.out.println(messag);
}
void processing() {
data=new byte[1024];
clientlistenpacket = new DatagramPacket(data,data.length);
try {
clientlistensocket.receive(clientlistenpacket);
go();
} catch (Exception e) {
System.out.println(e + " ClientlistenProcessing");
}
}
public void run() {
while (true) {
try {
processing();
} catch (Exception e) {
System.out.println(e + "Processing+run");
}
}
}
}
class ClientSpeak extends UDPClient {
DatagramPacket clientspeakpacket;
DatagramSocket clientspeaksocket;
InetAddress ipAddress;
Thread t;
public ClientSpeak(String username, String listening_port, String serverAddress, String servername) {
super(username, listening_port, serverAddress, servername);
try {
clientspeaksocket = new DatagramSocket();
} catch (Exception e) {
System.out.println(e + "ClientSpeak");
}
try {
String firstmessage = "Via:" + servername + "To:" + servername + "From:" + username + "Port:" + listening_port;
byte[] firstdata = firstmessage.getBytes();
ipAddress = InetAddress.getByName(serverAddress);
clientspeakpacket = new DatagramPacket(firstdata, firstdata.length, ipAddress, 5050);
clientspeaksocket.send(clientspeakpacket);
} catch (Exception e) {
System.out.println(e + "Clientspeak");
}
}
}
public class testC {
public static void main(String[] args) {
if (args.length == 4) {
String username = args[0].trim();
String listening_port = args[1].trim();
String serverAddress = args[2].trim();
String servername = args[3].trim();
ClientSpeak clientSpeak = new ClientSpeak(username, listening_port, serverAddress, servername);
ClientListen clientListen = new ClientListen(username, listening_port, serverAddress, servername);
}
}
}
但是它总是显示如下错误:
S
Via:STo:SFrom:nahPort:1
Nov 21, 2016 7:20:34 PM Stest run
SEVERE: null
java.net.BindException: Address already in use: Cannot bind
at java.net.DualStackPlainDatagramSocketImpl.socketBind(Native Method)
at java.net.DualStackPlainDatagramSocketImpl.bind0(DualStackPlainDatagramSocketImpl.java:84)
at java.net.AbstractPlainDatagramSocketImpl.bind(AbstractPlainDatagramSocketImpl.java:93)
at java.net.DatagramSocket.bind(DatagramSocket.java:392)
at java.net.DatagramSocket.<init>(DatagramSocket.java:242)
at java.net.DatagramSocket.<init>(DatagramSocket.java:299)
at java.net.DatagramSocket.<init>(DatagramSocket.java:271)
at Stest.run(test.java:41)
at java.lang.Thread.run(Thread.java:745)
我该怎么办?
问题是在服务器中的while循环内,您一直在尝试将新的数据报套接字绑定到端口5050
try {
sock = new DatagramSocket(5050);
} catch (SocketException ex) {
Logger.getLogger(test.class.getName()).log(Level.SEVERE, null, ex);
}
第二次,服务器读取并处理了UDP消息后,它将尝试进行绑定,并且将获得异常。
在while循环之前,您只需创建和绑定UDP套接字一次,然后将该套接字用于while循环中的整个通信。
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