[英]Why is it my code cannot run many clients in java multithreading?
为什么此代码不能累积许多客户端? 我是Java新手。 它仅可用于1个客户端。 谁能解释为什么它不支持套接字编程的多个客户端?
import java.net.*;
import java.io.*;
/**
* Demo Server: Contains a multi-threaded socket server sample code.
*/
public class ServerDemo extends Thread
{
final static int _portNumber = 5559; //Arbitrary port number
public static void main(String[] args)
{
try {
new ServerDemo().startServer();
} catch (Exception e) {
System.out.println("I/O failure: " + e.getMessage());
e.printStackTrace();
}
}
public void startServer() throws Exception {
ServerSocket serverSocket = null;
boolean listening = true;
try {
serverSocket = new ServerSocket(_portNumber);
} catch (IOException e) {
System.err.println("Could not listen on port: " + _portNumber);
System.exit(-1);
}
while (listening) {
handleClientRequest(serverSocket);
}
serverSocket.close();
}
private void handleClientRequest(ServerSocket serverSocket) {
try {
new ConnectionRequestHandler(serverSocket.accept()).run();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* Handles client connection requests.
*/
public class ConnectionRequestHandler implements Runnable{
private Socket _socket = null;
private PrintWriter _out = null;
private BufferedReader _in = null;
public ConnectionRequestHandler(Socket socket) {
_socket = socket;
}
public void run() {
System.out.println("Client connected to socket: " + _socket.toString());
try {
_out = new PrintWriter(_socket.getOutputStream(), true);
_in = new BufferedReader(new InputStreamReader(_socket.getInputStream()));
String inputLine, outputLine;
BusinessLogic businessLogic = new BusinessLogic();
outputLine = businessLogic.processInput(null);
_out.println(outputLine);
//Read from socket and write back the response to client.
while ((inputLine = _in.readLine()) != null) {
outputLine = businessLogic.processInput(inputLine);
if(outputLine != null) {
_out.println(outputLine);
if (outputLine.equals("exit")) {
System.out.println("Server is closing socket for client:" + _socket.getLocalSocketAddress());
break;
}
} else {
System.out.println("OutputLine is null!!!");
}
}
} catch (IOException e) {
e.printStackTrace();
} finally { //In case anything goes wrong we need to close our I/O streams and sockets.
try {
_out.close();
_in.close();
_socket.close();
} catch(Exception e) {
System.out.println("Couldn't close I/O streams");
}
}
}
}
/**
* Handles business logic of application.
*/
public static class BusinessLogic {
private static final int LoginUserName = 0;
private static final int LoginPassword = 1;
private static final int AuthenticateUser = 2;
private static final int AuthSuccess = 3;
private int state = LoginUserName;
private String userName = null;
private String userPassword = null;
public String processInput(String clientRequest) {
String reply = null;
try {
if(clientRequest != null && clientRequest.equalsIgnoreCase("login")) {
state = LoginPassword;
}if(clientRequest != null && clientRequest.equalsIgnoreCase("exit")) {
return "exit";
}
if(state == LoginUserName) {
reply = "Please Enter your user name: ";
state = LoginPassword;
} else if(state == LoginPassword) {
userName = clientRequest;
reply = "Please Enter your password: ";
state = AuthenticateUser;
} else if(state == AuthenticateUser) {
userPassword = clientRequest;
if(userName.equalsIgnoreCase("John") && userPassword.equals("doe")) {
reply = "Login Successful...";
state = AuthSuccess;
} else {
reply = "Invalid Credentials!!! Please try again. Enter you user name: ";
state = LoginPassword;
}
} else {
reply = "Invalid Request!!!";
}
} catch(Exception e) {
System.out.println("input process falied: " + e.getMessage());
return "exit";
}
return reply;
}
}
}
您没有在代码中启动线程。
代替
new ConnectionRequestHandler(serverSocket.accept()).run();
呼叫
new Thread(new ConnectionRequestHandler(serverSocket.accept())).start();
方法run()
您的Runnable
的类将被调用,当你开始你的线程,你不应该调用这个run()
直接方法。
相反,您应该通过以下方式创建线程实例
Thread myThread = new Thread(aRunnableInstance);
并启动它:
myThread.start();
您不是在启动新线程,而只是在主线程中运行RequestHandler代码。
查找Thread.start()
和Runnable.run()
之间的区别。 这个问题可能会有所帮助。
编辑:
您只是缺少告诉JVM创建一个新线程来执行您的Runnable代码的部分。 如果不调用Thread.start(),则当前(且仅)线程将一次忙于处理一个请求。 基本上,每个请求您需要一个线程。 有更高级的方法可以执行此操作(线程池等),但这应该可以帮助您入门。
private void handleClientRequest(ServerSocket serverSocket) {
try {
new Thread(ConnectionRequestHandler(serverSocket.accept())).start();
} catch (IOException e) {
e.printStackTrace();
}
}
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