我在下面收到此错误。如果我取出代码的执行程序服务部分，我的代码可以工作。因此，将其归结为大致几行代码。但我将包括必要的客户端和服务器代码
Error in connecting to server: 20999
java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at client.Client_Controller.connect(Client_Controller.java:32)
at client.Client_Controller.<init>(Client_Controller.java:23)
at client.Client_UI.<init>(Client_UI.java:29)
at client.Client_UI$1.run(Client_UI.java:169)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at client.Client_Controller.outputStream(Client_Controller.java:45)
at client.Client_Controller.<init>(Client_Controller.java:24)
at client.Client_UI.<init>(Client_UI.java:29)
at client.Client_UI$1.run(Client_UI.java:169)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
以下是服务器代码：
public Server(int port, Client_Handler_Factory handlerFactory, ExecutorService executor) throws IOException {
Objects.requireNonNull(port);
Objects.requireNonNull(executor);
this.serverSocket = new ServerSocket(port);
this.handlerFactory = handlerFactory;
this.executor = executor;
}
public void start() {
executor.submit(new Runnable() {
@Override
public void run() {
try {
listen();
}
catch (IOException ex) {
System.out.println("An exception occurred while the server was listening");
ex.printStackTrace();
}
}
});
}
public void listen() throws IOException {
synchronized (this) {
if (listening) {
throw new IllegalStateException(
"The server has already started listening");
}
listening = true;
}
try {
while (!closed) {
socket = serverSocket.accept();
executor.submit(new Runnable() {
public void run() {
delegateToHandler(socket);
}
});
}
}
catch (SocketException ex) {
if (closed)
System.out.println("Socket is closed!");
else
throw ex;
}
}
private void delegateToHandler(Socket socket) {
try {
handlerFactory.createHandler(socket).handle();
} catch (IOException ex) {
System.out
.println("Exception occured while handling the connection to "
+ socket.getInetAddress());
}
finally {
try {
socket.close();
} catch (IOException ex) {
System.out.println("Exception occured while trying to close the connection to "
+ socket.getInetAddress());
}
}
}
public void close() throws IOException {
if (!closed) {
closed = true;
serverSocket.close();
executor.shutdown();
}
}
}
以下是服务器的主要方法：
public static void main(String... args) throws Exception {
ExecutorService executor = Executors.newCachedThreadPool();
System.out.println("Server has started");
try (Server server = new Server(20999, new ClientName_Handler.Factory(), executor))
{
server.start();
}
}
}
以下是与服务器连接的客户端代码：
Client_Controller() {
this.connect(hostName, port);
this.outputStream();
this.inputStream();
}
private void connect(String hostName, int port) {
try {
socket = new Socket(hostName, port);
} catch (UnknownHostException ex) {
System.out.println("Host was not found: " + hostName);
} catch (IOException ex) {
System.out.println("Error in connecting to server: " + port);
ex.printStackTrace();
}
}
private void outputStream() {
try {
out = new DataOutputStream(socket.getOutputStream());
outObj = new ObjectOutputStream(socket.getOutputStream());
} catch (IOException ex) {
System.out.println("Output stream failure");
}
}
private void inputStream() {
try {
in = new DataInputStream(socket.getInputStream());
inObj = new ObjectInputStream(socket.getInputStream());
} catch (IOException ex) {
System.out.println("Input stream failure");
}
}
public void closeConnection() throws IOException {
try {
this.sendMessage("Client_Close");
}
finally {
try {
out.close();
}
finally {
try {
in.close();
}
finally {
socket.close();
}
}
}
}
public void sendMessage(String message) throws IOException {
try {
out.writeUTF(message);
}
finally {
out.flush();
}
}
public String receiveMessage() {
String input = null;
try {
input = in.readUTF();
} catch (IOException ex) {
System.out.println("Error receving the message from the server");
}
return input;
}
public Object receiveObject(String message) {
Object input = null;
try {
sendMessage(message);
input = inObj.readObject();
System.out.println(input);
} catch (IOException | ClassNotFoundException ex) {
System.out.println("Error receving the message from the server");
}
return input;
}
}
下面是代码行，如果我删除将允许客户端连接。这些代码行可以在方法start（）和listen（）下的服务器类中找到。非常感谢所有帮助。
executor.submit(new Runnable() {
@Override
public void run() {
try {
listen();
}
catch (IOException ex) {
System.out.println("An exception occurred while the server was listening");
ex.printStackTrace();
}
}
});
executor.submit(new Runnable() {
public void run() {
delegateToHandler(socket);
}
});
答案 0 :(得分：0)
当您通过ExecutorService运行listen（）方法时，它允许start（）返回，这会导致您的try-with-resources块退出并关闭服务器套接字，因此您的客户端无需连接