基本的Java Web服务器 - 接收SocketException：连接重置

Question

我试图创建一个基本的HTTP/1.1兼容的Web服务器，它支持持久连接的简单GET请求。我得到一个SocketException：在第61行发生连接重置错误（如果（行== == || line.equals（“”））。我测试它通过运行它，然后将我的浏览器指向本地主机portnumber。当我用一个带有多个图像的页面测试它时，似乎只有一个请求正在异常发生前处理，但我不确定有什么问题，因为这是我第一次尝试在任何类型的套接字编程中使用。除去DataOutputStream类后，我更新的代码：

import java.io.BufferedReader; 
import java.io.ByteArrayOutputStream; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.InputStreamReader; 
import java.io.ObjectOutputStream; 
import java.io.PrintWriter; 
import java.net.ServerSocket; 
import java.net.Socket; 
import java.net.URI; 
import java.net.URISyntaxException; 
import java.text.SimpleDateFormat; 
import java.util.Date; 
import java.util.HashMap; 
import java.util.StringTokenizer; 

public class webserve 
{ 
    public static void main(String[] args) throws Exception 
    { 
     String rootPath = "~/Documents/MockWebServerDocument/"; 
     int port = 10000; 

     if(rootPath.startsWith("~" + File.separator)) 
     { 
      rootPath = System.getProperty("user.home") + rootPath.substring(1); 
     } 

     String requestLine=""; 
     StringTokenizer tokens=null; 
     String line, command; 
     Date date = new Date(); 
     String connectionStatus=""; 


     //Create new server socket listening on specified port number 
     ServerSocket serverSocket = new ServerSocket(port); 

     while(true) 
     { 
      //Wait for a client to connect and make a request 
      Socket connectionSocket = serverSocket.accept(); 
      System.out.println("Socket opened"); 

      //Input stream from client socket 
      BufferedReader incomingFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream())); 
      //PrintWriter to send header to client socket 
      PrintWriter outgoingHeader = new PrintWriter(connectionSocket.getOutputStream(),true); 
      //OutputStream to send file data to client socket 
      ObjectOutputStream outgoingFile = new ObjectOutputStream(connectionSocket.getOutputStream()); 
      //Date format for HTTP Header 
      SimpleDateFormat HTTPDateFormat = new SimpleDateFormat("EEE MMM d hh:mm:ss zzz yyyy"); 


      //Create a HashMap to store the request header information 
      HashMap<String,String> requestHeader = new HashMap<String,String>(); 

      while(connectionSocket.isConnected()) 
      { 
       //requestHeader.clear(); 

       while((line = incomingFromClient.readLine()) != null) 
       { 
        if(line.isEmpty()) 
        { 
         break; 
        } 
        //If this is the first line of the request, i.e doesnt contain a colon 
        if(!(line.contains(":"))) 
        { 
         requestLine = line; 
         requestHeader.put("Request", requestLine); 
        } 
        else 
        { 
         //Otherwise, find the colon in the line and create a key/value pair for the HashMap 
         int index = line.indexOf(':')+2; 
         String header = line.substring(0,index-1); 
         line = line.substring(index).trim(); 

         requestHeader.put(header, line); 

         System.out.println(header + " " + line); 
        } 
       } 

       connectionStatus = (String)requestHeader.get("Connection:"); 
       requestLine = (String)requestHeader.get("Request"); 

       System.out.println("RequestLine: " + requestLine); 

       if(!requestLine.equals("")||!(requestLine.equals(null))) 
       { 
        tokens = new StringTokenizer(requestLine); 

        command = tokens.nextToken(); 
        String filename = tokens.nextToken(); 
        filename = cleanUpFilename(filename); 
        String fullFilepath = rootPath + filename; 
        System.out.println("Full FilePath: " + fullFilepath); 

        File file = new File(fullFilepath); 

        //Get the number of bytes in the file 
        int numOfBytes=(int)file.length(); 

        //Open a file input stream using the full file pathname 
        FileInputStream inFile = new FileInputStream(fullFilepath); 

        //Create byte array to hold file contents 
        byte[] fileInBytes = new byte[numOfBytes]; 

        inFile.read(fileInBytes,0,numOfBytes); 

        inFile.close(); 


        //Write the header to the output stream 
        outgoingHeader.print("HTTP/1.1 200 OK\r\n"); 
        outgoingHeader.print("Date: " + HTTPDateFormat.format(date)+"\r\n"); 
        outgoingHeader.print("Server: BC-Server\r\n"); 
        outgoingHeader.print("Last-Modified: " + HTTPDateFormat.format(file.lastModified())+"\r\n"); 
        outgoingHeader.print("Connection: keep-alive\r\n"); 
        outgoingHeader.print("Content-Length: " + numOfBytes); 
        outgoingHeader.print("\r\n\r\n");    

        //When the header has been printed, write the byte array containing the file 
        //to the output stream 
        outgoingFile.writeObject(fileInBytes); 

        if(!(connectionStatus.equals("keep-alive"))) 
        { 
         System.out.println("Closing: " + connectionStatus); 
         outgoingHeader.close(); 
         outgoingFile.close(); 
         break; 
        } 
        else 
         continue; 

       }  

      } 

     } 
    } 

    public static String cleanUpFilename(String filename) 
    { 
     //If there is a "/" at the start of the filename, then remove it 
     if(filename.charAt(0) == '/') 
     { 
      filename = filename.substring(1); 
     } 

     //If we are given an absolute URI request, strip all characters 
     //before the third "/" 
     if(filename.startsWith("http://")); 
     { 
      try 
      { 
       URI httpAddress = new URI(filename); 

       //Get the path from the supplied absolute URI, that is remove 
       //all character before the third "/" 
       filename = httpAddress.getPath(); 

       //Again, we may have to trim this modified address if there is an 
       //extra "/" at the start of the filename 
       if(filename.charAt(0) == '/') 
       { 
        filename = filename.substring(1); 
       } 
      } 
      catch (URISyntaxException e) 
      {     
       e.printStackTrace(); 
      } 
     } 

     return filename; 
    } 

}

这里是我的错误跟踪：

Exception in thread "main" java.net.SocketException: Connection reset 
    at java.net.SocketInputStream.read(SocketInputStream.java:185) 
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:282) 
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:324) 
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:176) 
    at java.io.InputStreamReader.read(InputStreamReader.java:184) 
    at java.io.BufferedReader.fill(BufferedReader.java:153) 
    at java.io.BufferedReader.readLine(BufferedReader.java:316) 
    at java.io.BufferedReader.readLine(BufferedReader.java:379) 
    at webserve.main(webserve.java:61) 

任何帮助将不胜感激，因为我在完全损失。

Answer 1

尝试使用telnet，wget或curl而不是chrome来测试连接，因为您可以控制双方的TCP/IP连接。

我认为您的网络客户端正在关闭它的连接，并且您尝试再次从该套接字读取（是的，即使isConnected()在远程方关闭连接时也会引发此错误）。我也很抱歉地说，没有简单的方法来对付这个问题，而是抓住例外情况并优雅地处理它。

这是一个经常发生在同步套接字上的问题。尝试使用java.nio通道和选择器。

Answer 2

您不能使用DataOutputStream，它用于Java-Java通信。尝试Writer用于编写标题，以及用于编写文件内容的原始OutputStream。

发生什么事是浏览器看到无效的响应，并关闭连接。服务器仍在写信给客户端，客户端响应RST，因为连接已经结束。

Answer 3

同时使用多个输出流是非常成问题的。在这种情况下，您不应创建ObjectOutputStream，直到您确定要写入对象并且已经写入并刷新标题为止，因为ObjectOutputStream会将写入标头写入输出中，在您的当前代码中它将出现在任何标题之前，可能会导致客户bar喝。

通常，SocketException: Connection Reset通常表示您已写入已由对等方关闭的连接。在这种情况下，对等端是客户端，而客户端是Web浏览器，它可以表示任何东西，例如，用户停止加载页面，他浏览了一下，退出浏览器，关闭了标签页。这不是你的问题。只需关上插座并忘记它。

出于同样的原因，你的服务器也应该设置一个合理的读取超时时间，比如说10-30秒，并且如果它触发，就进行保护。

Answer 4

你的服务器最明显的问题是它不是多线程的。重新阅读你对问题的描述后，这似乎是根本原因。每个连接需要一个线程。在serverSocket.accept()之后，创建一个新的线程来处理connectionSocket。

while(true) 
    { 
     //Wait for a client to connect and make a request 
     Socket connectionSocket = serverSocket.accept(); 

     new Thread() 
     { 
      public void run() 
      { 
       //Input stream from client socket 
       BufferedReader incomingFromClient = ... 

       etc 

      } 
     }.start();