如何读取Server Socket JAVA中的所有Inputstream

Question

我在我的一个项目中使用Java.net.我写了一个从客户端获取inputStream的App Server.但有时我的(缓冲)InputStream无法获取客户端发送到我的服务器的所有OutputStream.我怎么能写一个等待或类似的东西,我的InputStream获取客户端的所有OutputStream？

(我的InputStream不是字符串)

private Socket clientSocket;
private ServerSocket server;
private BufferedOutputStream outputS;
private BufferedInputStream inputS;
private InputStream inBS;
private OutputStream outBS;

server = new ServerSocket(30501, 100);
clientSocket = server.accept();

public void getStreamFromClient()  {
    try {
        outBS = clientSocket.getOutputStream();
        outputS = new BufferedOutputStream( outBS);
        outputS.flush();

        inBS = clientSocket.getInputStream();
        inputS = new BufferedInputStream( inBS );

    } catch (Exception e) {
        e.printStackTrace();
    }
}

谢谢.

Answer 1

您遇到的问题与TCP流性质有关.

您从服务器发送100字节(例如)的事实并不意味着您第一次阅读时将在客户端中读取100字节.也许从服务器发送的字节到达客户端的几个TCP段.

您需要实现一个循环,您可以在其中读取整个消息.让我举一个例子DataInputStream而不是BufferedinputStream.给你一个例子非常简单的东西.

假设您事先知道服务器要发送100字节的数据.

在客户端你需要写:

byte[] messageByte = new byte[1000];
boolean end = false;
String dataString = "";

try 
{
    DataInputStream in = new DataInputStream(clientSocket.getInputStream());

    while(!end)
    {
        int bytesRead = in.read(messageByte);
        dataString += new String(messageByte, 0, bytesRead);
        if (dataString.length == 100)
        {
            end = true;
        }
    }
    System.out.println("MESSAGE: " + dataString);
}
catch (Exception e)
{
    e.printStackTrace();
}

现在,通常预先知道一个节点(此处的服务器)发送的数据大小.然后,您需要为服务器与TCP通信的客户端(或任何两个节点)之间的通信定义自己的小协议.

最常见也很简单的是定义TLV:Type,Length,Value.因此,您定义从服务器发送到客户端的每条消息都带有:

• 1字节表示类型(例如,它也可以是2或其他).
• 1个字节(或其他)的消息长度
• 值的N个字节(N表示长度).

因此,您知道必须至少接收2个字节,而使用第二个字节,您知道需要读取多少个字节.

这只是一个可能的协议的建议.你也可以摆脱"类型".

所以它会是这样的:

byte[] messageByte = new byte[1000];
boolean end = false;
String dataString = "";

try 
{
    DataInputStream in = new DataInputStream(clientSocket.getInputStream());
    int bytesRead = 0;

    messageByte[0] = in.readByte();
    messageByte[1] = in.readByte();

    int bytesToRead = messageByte[1];

    while(!end)
    {
        bytesRead = in.read(messageByte);
        dataString += new String(messageByte, 0, bytesRead);
        if (dataString.length == bytesToRead )
        {
            end = true;
        }
    }
    System.out.println("MESSAGE: " + dataString);
}
catch (Exception e)
{
    e.printStackTrace();
}

以下代码编译并且看起来更好.假设提供长度的前两个字节以二进制格式到达,在网络结束(big endian)中.不关注消息其余部分的不同编码类型.

import java.nio.ByteBuffer;
import java.io.DataInputStream;
import java.net.ServerSocket;
import java.net.Socket;

class Test
{
    public static void main(String[] args)
    {
        byte[] messageByte = new byte[1000];
        boolean end = false;
        String dataString = "";

        try 
        {
            Socket clientSocket;
            ServerSocket server;

            server = new ServerSocket(30501, 100);
            clientSocket = server.accept();

            DataInputStream in = new DataInputStream(clientSocket.getInputStream());
            int bytesRead = 0;

            messageByte[0] = in.readByte();
            messageByte[1] = in.readByte();
            ByteBuffer byteBuffer = ByteBuffer.wrap(messageByte, 0, 2);

            int bytesToRead = byteBuffer.getShort();
            System.out.println("About to read " + bytesToRead + " octets");

            //The following code shows in detail how to read from a TCP socket

            while(!end)
            {
                bytesRead = in.read(messageByte);
                dataString += new String(messageByte, 0, bytesRead);
                if (dataString.length() == bytesToRead )
                {
                    end = true;
                }
            }

            //All the code in the loop can be replaced by these two lines
            //in.readFully(messageByte, 0, bytesToRead);
            //dataString = new String(messageByte, 0, bytesToRead);

            System.out.println("MESSAGE: " + dataString);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}