java 如何从服务器向客户端发送消息
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How to send message from server to client
提问by tinaw25
I am trying to make an chatprogram in Java, when I send message on the client side the server side gets the message. But when I send from the server side to the client it do not get the message.
我正在尝试用 Java 制作一个聊天程序，当我在客户端发送消息时，服务器端会收到消息。但是当我从服务器端发送到客户端时，它没有收到消息。
I cannot see what I am doing wrong.
我看不出我做错了什么。
The server side code:
服务器端代码：
private void serverStart(){
textArea.append("Starting server " + " \n");
try {
serverSocket = new ServerSocket(4444);
textArea.append("Waiting for Clients " + " \n");
//Reading message from the client
socket = serverSocket.accept();
textArea.append("Client Connected " + "\n");
//Send message to client
out = new PrintWriter(socket.getOutputStream());
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
while (true)
{
messageFromClient = in.readLine();
whileChat(messageFromClient);
}
} catch(IOException ioExecption) {
ioExecption.printStackTrace();
}
}
private void whileChat(String messageFromClient) {
showMessage(messageFromClient);
System.out.println("Message from client : " + messageFromClient);
}
protected static void showMessage(final String message) {
SwingUtilities.invokeLater(
new Runnable(){
public void run()
{
Gui.consoleTextArea.append(message + "\n");
}
});
}
public static void sendMessage(String message) {
out.println(message);
showMessage(name + " : " + message + "\n");
}
The Client side :
客户端：
private void connectToServer() {
try {
socket = new Socket("localhost", 4444);
} catch (UnknownHostException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
Thread clientThread = new Thread(new Runnable() {
@Override
public void run() {
try {
// attach to socket's output stream with auto flush turned on
//Send message to the server
out = new PrintWriter(socket.getOutputStream(),
true);
//Get return message from server
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
messageFromServer = in.readLine();
whileChatting(messageFromServer);
} catch (Exception e) {
e.printStackTrace();
}
}
});
clientThread.start();
}
private void whileChatting(String messageFromServer) {
showMessage(messageFromServer);
System.out.println("Message from server to client " + messageFromServer);
}
public static void Send(String msg) {
out.println(name + " : " + msg);
showMessage(name + " : " + msg + "\n");
}
protected static void showMessage(final String message) {
SwingUtilities.invokeLater(
new Runnable(){
public void run(){
Gui.consoleTextArea.append(message);
}
});
}
Hope someone could help me with this problem.
希望有人能帮我解决这个问题。
采纳答案by Little Santi
You could perform a flush on the PrintWriter immediately after each println, or even better: Instance the PrintWriter with autoFlush=true:
您可以在每次 println 之后立即对 PrintWriter 执行刷新，或者甚至更好：使用 autoFlush=true 实例化 PrintWriter：
out = new PrintWriter(socket.getOutputStream(), true);
In this way, each time you call println, printf, or format, the PrintWriter will perform a flush of the buffer at the end.
这样，每次调用println、printf、 或 时format， PrintWriter 都会在最后执行缓冲区刷新。
回答by chengpohi
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
This line is always waiting the client output, and your client also doesn't send message to server.
此行始终在等待客户端output，您的客户端也不会向 发送消息server。
Attention: both your serverand clientnot read user input.
注意：您server和client不读取用户输入。
