java - ServerSocket循环中没有接收到数据

Question

我使用 ServerSocket 在 while 循环中从客户端获取数据，它在第一次运行时有效，但在第二轮后失败。

我做了一些搜索，但仍然无法弄清楚发生了什么。

服务器端代码

package com.gorilla.main;

import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server2 {

    public static void main(String[] args) throws Exception {

        ServerSocket serverSocket = new ServerSocket(44444);

        while(true){

        System.out.println("another round");

        Socket socket  = serverSocket.accept();
        InputStream inputStream = socket.getInputStream();

        System.out.println("available: "+ inputStream.available());

        byte[] b = new byte[inputStream.available()];

        inputStream.read(b);

        System.out.println(new String(b));
        System.out.println("=======================");

        socket.close();
        }
    }
}

客户端代码

package com.gorilla.main;

import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;

public class Client2 {

    public static void main(String [] args) throws Exception{

        Socket socket = new Socket("127.0.0.1", 44444);
        String s = "Hello World";
        byte [] b = s.getBytes();
        socket.getOutputStream().write(b);;
        socket.close();

    }
}

以及我运行客户端 3 次后服务器端控制台的输出。

another round
available: 11
Hello World
=======================
another round
available: 0

=======================
another round
available: 0

=======================
another round

如有任何建议，我们将不胜感激。谢谢。

Answer 1

您使用 InputStream.available()调整缓冲区的大小，这不是从套接字读取数据的方式。您应该分配一个缓冲区(通常静态调整大小，或者可以配置)并循环读取

// server code
byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = in.read(buffer)) > -1) {
  // do something
}

InputStream.available() 的 Javadoc:

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

如果您的协议(protocol)是基于文本的，您可以将套接字的输入流包装在 Scanner 中。因此循环就变成了

while (scanner.hasNextLine()) {
  String line = scanner.next();
}