Java 套接字 - 读取和写入
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Java socket - Read & Write
提问by Shlomi
The problem: Client doesn't receive any message.
问题：客户端没有收到任何消息。
Here is the full code for both client and server:
这是客户端和服务器的完整代码：
CLIENT
客户
public class Client extends Socket{
public Client(String hostName, int port) throws UnknownHostException, IOException {
super(hostName,port);
BufferedReader in = new BufferedReader(new InputStreamReader(getInputStream()));
while(true) {
String line = in.readLine();
System.out.println("Text received: " + line);
}
}
SERVER
服务器
public final class Server extends ServerSocket{
public Server(int port) throws IOException {
super(port);
System.out.println("Server waiting for client 1");
Socket client1 = accept();
PrintWriter writer = new PrintWriter(client1.getOutputStream(), true);
writer.write("Hello user 1");
System.out.println("Server waiting for client 2");
Socket client2 = accept();
PrintWriter writer2 = new PrintWriter(client2.getOutputStream(), true);
writer2.write("Hello user 2");
System.out.println("Clients connected");
}
- I start the server to listen to port 4444
- I start the clients with hostname of "localhost" and port 4444
- 我启动服务器监听4444端口
- 我以“localhost”的主机名和端口 4444 启动客户端
回答by Nerdizzle
You have to include a newline character at the end of the message, and also flush the PrintWriter if the connection is not immediately altered, forcing an automatic flush:
你必须在消息的末尾包含一个换行符，如果连接没有立即改变，还要刷新 PrintWriter，强制自动刷新：
writer.write("Hello user 1\n");
writer.flush();
EDIT:
编辑：
It is possible to enable automatic flushing on a PrintWriter using the constructor new PrintWriter(someOutputStream, true)
可以使用构造函数在 PrintWriter 上启用自动刷新 new PrintWriter(someOutputStream, true)
However, as explained in the documentation:
但是，如文档中所述：
if automatic flushing is enabled it will be done only when one of the println, printf, or format methods is invoked, rather than whenever a newline character happens to be output
如果启用了自动刷新，则只有在调用 println、printf 或 format 方法之一时才会执行，而不是在刚好输出换行符时执行
This means that even with automatic flushing, the PrintWriter would still have to be manually flushed after writeis called, and a newline character (\n) would still have to be included at the end of the string.
这意味着即使使用自动刷新，在write调用PrintWriter 后仍然必须手动刷新，并且\n仍然必须在字符串的末尾包含换行符 ( )。
EDIT 2:
编辑2：
Here is a small example of a fully functional client/server application:
这是一个功能齐全的客户端/服务器应用程序的小例子：
Client:
客户：
public static void main(String[] args){
try{
Socket socket = new Socket(HOST_ADDRESS, PORT);
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
System.out.println(bufferedReader.readLine());
bufferedReader.close();
socket.close();
}catch(IOException e){}
}
Server:
服务器：
public static void main(String[] args){
try{
ServerSocket serverSocket = new ServerSocket(PORT);
Socket socket = serverSocket.accept();
PrintWriter printWriter = new PrintWriter(socket.getOutputStream());
printWriter.write("Hello user!\n");
printWriter.flush();
printWriter.close();
socket.close();
serverSocket.close();
}catch(IOException e){}
}
