如何解决Java套接字聊天程序聊天成员突然离开房间，没有错误
我们用Java编写了套接字聊天程序。但是，当有两个或更多聊天成员时，我们会发生一个问题。如果有名为A，B和C的成员（按字母顺序输入），则当A（或B）离开会议室时，最后一个成员（C）与A（或B）一起离开会议室而没有错误。如果有成员D，则前一个成员离开房间，最后一个成员（此案例成员D）与前一个成员一起离开房间而没有错误。我们该如何解决？
//处理发生错误的错误//
A进入> B进入> C进入> D进入> A或B或C离开（为什么D也离开？？？
服务器
public class Server {
public static final int PORT = 7777;
private ServerSocket serverSocket;
private Socket socket;
private ServerGUI gui;
private String msg;
private int count = 0;
private int NMC=0;
private Map<String,DataOutputStream> clientsMap = new HashMap<String,DataOutputStream>();
public final void setGUI(ServerGUI gui) {
this.gui = gui;
}
public void setting() throws IOException {
Collections.synchronizedMap(clientsMap);
serverSocket = new ServerSocket(PORT);
String hostAddress = InetAddress.getLocalHost().getHostAddress();
while (true) {
System.out.println("waiting connection - " + hostAddress + ":" + PORT);
socket = serverSocket.accept();
System.out.println("connected from" + socket.getInetAddress());
Receiver receiver = new Receiver(socket);
receiver.start();
}
}
public void addClient(String name,DataOutputStream out) throws IOException {
clientsMap.put(name,out);
sendMessage(name + "entered\n");
gui.appendMsg(name + "entered\n");
count++;
gui.appendMsg("joining member : " + count + "\n");
}
public void sendMessage(String msg) {
Iterator<String> member = clientsMap.keySet().iterator();
String key = "";
while (member.hasNext()) {
key = member.next();
try {
clientsMap.get(key).writeUTF(msg);
} catch (IOException e) {
e.printStackTrace();
}
}
}
class Receiver extends Thread {
private DataInputStream in;
private DataOutputStream out;
private String name;
public Receiver(Socket socket) throws IOException {
out = new DataOutputStream(socket.getOutputStream());
in = new DataInputStream(socket.getInputStream());
name = in.readUTF();
if (count != 0) {
NMC=NameMatch(name);
}
if (NMC == 1 || count == 0) {
addClient(name,out);
} else {
out.writeUTF("not available");
socket.close();
out.close();
in.close();
}
}
public void run() {
try {
while (in != null) {
msg = in.readUTF();
sendMessage(msg);
gui.appendMsg(msg);
}
} catch (IOException e) {
try {
if (NMC == 0) {
socket.close();
in.close();
out.close();
NMC++;
} else {
socket.close();
in.close();
out.close();
clientsMap.remove(name);
count--;
gui.appendMsg(name + "has left.\n");
gui.appendMsg("joining member : " + count + "\n");
sendMessage(name + "has left.\n");
}
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}
public int NameMatch(String name) {
Iterator<String> member = clientsMap.keySet().iterator();
String key = "";
while (member.hasNext()) {
int i = 0;
if (i == count) {
break;
}else{
key = member.next();
if (key.equals(name)) {
return 0;
}
}
i++;
}
return 1;
}
public static void main(String[] args) throws IOException {
Server server = new Server();
server.setting();
}
}
''' 客户
package chat.client;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import javax.swing.JOptionPane;
public class Client {
private Socket socket;
private DataInputStream in;
private DataOutputStream out;
private ClientGUI gui;
private String msg;
private String Name;
private int PORT = 0;
private String IP = "";
public final void setGUI(ClientGUI gui) {
this.gui = gui;
}
class connect extends Thread {
public connect() {
try {
socket = new Socket(IP,PORT);
System.out.println("Connected.");
out = new DataOutputStream(socket.getOutputStream());
in = new DataInputStream(socket.getInputStream());
out.writeUTF(Name);
if (in.readUTF().equals("not available")) {
out.close();
in.close();
socket.close();
JOptionPane.showMessageDialog(null,"not available");
System.exit(1);
}
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
try {
while (in != null) {
msg = in.readUTF();
gui.appendMsg(msg);
}
} catch (IOException e) {
try {
out.close();
in.close();
socket.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}
public static void main(String[] args) throws IOException {
Client client = new Client();
client.setConnect();
}
public void setConnect() {
connect c = new connect();
c.start();
}
public void sendMessage(String msg) {
try {
out.writeUTF(msg);
} catch (IOException e) {
e.printStackTrace();
}
}
public void setNickname(String Name) {
this.Name = Name;
}
public void Port(int port) {
this.PORT = port;
}
public void Ip(String ip) {
this.IP = ip;
}
}
解决方法
在Server.Receiver类中，您没有保留对连接的客户端套接字的引用。这意味着当run方法使用以下命令关闭套接字时：
socket.close();
它实际上正在使用包含的socket类中的Server变量，该变量恰好是已连接的最新用户的连接。这意味着当A，B或C中的任何一个离开时，D都会断开连接。
您可以通过简单地从socket.close()方法中删除对Receiver.run的调用来解决此问题。当您关闭与之关联的输入或输出流时，套接字将关闭。
避免将来出现类似错误的提示：
-
尽可能避免使用实例变量。如果
Server.socket是局部变量，则错误从一开始就很明显，因为首先没有要使用的“套接字”变量。Socket socket = serverSocket.accept(); System.out.println("connected from" + socket.getInetAddress()); Receiver receiver = new Receiver(socket); -
创建嵌套类时，最好先将它们设为
static：static class Receiver extends Thread {这可以防止意外使用封闭对象实例。发现需要使用封闭的对象实例时，始终可以删除“静态”修饰符。
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