Software Connection reset 和Software caused connection abort: recv failed 的一些錯誤

除了那些我在網上搜集的造成的因素，例如一端關閉，另一端沒關閉；資料正發送時Server關閉，而Client無法從輸入資料流中讀取，還有什麼資料庫的服務，還有什麼IIS的服務需要關閉。

                 個人的理解，如果按照規範或者書上例子編寫，錯誤可能有如下，雖然根本原因和上述是相同的，但具體的導致原因可能不同。

                 用戶端，發送資料時的結束符，一般以“\n”結束，如果忘記使用可能會產生該錯誤，或者一直等待，對於本地的伺服器，自己編寫的，加一個就可以了，但是如果對網路上的伺服器，必須加兩個。

                連接埠的佔用，比如你正在開著瀏覽器，結果編程式使用80連接埠，必然會導致此錯誤的產生。

                伺服器或者用戶端的檔案目錄，當讀寫時，找不到正確的目錄，並非一定會告訴你是IO錯誤，而可能反映是Socket錯誤，所以這個也要務必檢查。

                關於在用戶端和伺服器，socket關閉，最容易產生此類錯誤，關閉的時機不對，就會出錯，不關閉也會出錯，例如，伺服器端不關閉socket，伺服器端不會報錯，但是對於用戶端來說，如果用infromstream讀取，當資料發送完畢時，再次readline，便會出錯，正常情況下，在伺服器端關閉socket，此時用戶端的讀取會讀取到null，而不會產生錯誤。

                就是這樣的。

import java.io.*;
import java.util.*;
import java.net.*;

public class WebServer {

// the work content of the Server
final static String path = "F:\\work\\SSD8\\EX1-lab";


//the edition of the HTTP
final static String ipEdition = "HTTP/1.1";

//the communication port of the Server
final static int port = 80;

//main method to respond for a client
public static void main(String argv[]){

try{
System.out.println("The Server start!\n");

ServerSocket listenSocket = new ServerSocket(port);

while(true){
   Socket connectionSocket = listenSocket.accept();
   respondToClient(connectionSocket);
}

}catch(SocketException e){
   System.out.println("socket error in Server\n" + e.getMessage());
}catch(IOException e){
   System.out.println("io error in Server\n" + e.getMessage());
}
}


// method to respond cient, including to receice and send the data
public static void respondToClient(Socket connectionSocket) throws IOException,SocketException

{
String requestMessagegetline;
String filename;
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
requestMessagegetline = inFromClient.readLine();
StringTokenizer token = new StringTokenizer(requestMessagegetline," ");
if(token.nextToken().equals("GET")){
   filename = path + token.nextToken();
   File file = new File(filename);
   if(file.exists()){
    if(ipEdition.equals(token.nextToken())){
     int numOfBytes = (int)file.length();
     FileInputStream inFile = new FileInputStream(filename);
     byte[] fileInBytes = new byte[numOfBytes];
     inFile.read(fileInBytes);
   
     System.out.println("ready send the head\n");
     outToClient.writeBytes("HTTP/1.0 200 Document Follow\r\n");
     if(filename.endsWith("html"))
      outToClient.writeBytes("Content-Type: text/html\r");
     if(filename.endsWith(".gif"))
      outToClient.writeBytes("Content-Type: image/gif\r");
     if(filename.endsWith(".jpg"))
      outToClient.writeBytes("Content-Type: image/jpeg\r");
     outToClient.writeBytes("Content-length: " + numOfBytes + "\r\n");
     outToClient.writeBytes("\r\n");
    
     System.out.println("finish send the head\n");
     System.out.println("ready send the filedata\n");
     outToClient.write(fileInBytes,0,numOfBytes);
     System.out.println("finish the data send\n");
    }else{
     outToClient.writeBytes("HTTP/1.0 505 Version Not Supported\r\n");
    }
   }else{
    outToClient.writeBytes("HTTP/1.0 404 Not Found\r\n");
   }
}else{
   outToClient.writeBytes("HTTP/1.0 400 Bad Request\r\n");
}
System.out.println("closed\n");
connectionSocket.close();
}
}

import java.io.*;
import java.net.*;
import java.util.*;

//content:EX1,The client to send message to server to get the head and the data
public class TCPClient {

// the communication port number
final static int portNumber = 5678;

final String pathOfFile = "F:\\work\\SSD8\\EX1-lab\\";

// the data packet of the head from the Server
public String packetHead;

//the data in the packet of the entity
public String fileData;

// name of the Server
public String serverName;

//The IP proticol edition of the user's
public String ipEdition;

//main method to run the program
public static void main(String argv[]){

TCPClient client = new TCPClient();

String userRequest = null;

if(argv[0] != null)client.serverName = argv[0];
else return;

try{

   System.out.println("Enter the request for the Server:");
   BufferedReader inFromUser = new BufferedReader(
     new InputStreamReader(System.in));
   userRequest = inFromUser.readLine();
  
   if(client.connectToServer(userRequest))
    client.writeToFile();
  
   System.out.println("Finish");
  
}catch(SocketException e){
   System.out.println("socket error in Client!" + e.getMessage());
}catch(IOException e){
   System.out.println("io exception in Client!" + e.getMessage());
}
}

//initialize the data of Client
public TCPClient(){
packetHead = "";
fileData = "";
serverName = null;
ipEdition = null;
}

// write the data from the Sever to a specific file
public void writeToFile()throws IOException{
System.out.println("Enter the filename you want to save:");
BufferedReader inFromUser = new BufferedReader(
    new InputStreamReader(System.in));

File file = new File(pathOfFile + inFromUser.readLine());
FileWriter fileWrites = new FileWriter(file);
fileWrites.write(fileData);
fileWrites.close();
}

//create Socket to the Server and send it the request by user
// it will get a data packet, separate the data and initialize some valubal of the Client
public boolean connectToServer(String requestForServer)throws IOException{

Socket clientSocket = new Socket(serverName,portNumber);
if(clientSocket.isConnected()){
   DataOutputStream outToServer = new DataOutputStream(
     clientSocket.getOutputStream());
   BufferedReader inFromServer = new BufferedReader(
     new InputStreamReader(clientSocket.getInputStream()));

   outToServer.writeBytes(requestForServer + "\r\n" + "\r\n");

   System.out.println("connect!");
   System.out.println("From Server :");
  
   String S = inFromServer.readLine();
   while(S != null && !S.startsWith("<") ){
    packetHead += S + "\r";
    S = inFromServer.readLine();
   }
   System.out.println(packetHead);
  
   StringTokenizer token = new StringTokenizer(packetHead," ");
   token.nextToken();
   String conditionKey = token.nextToken();
  
   if(conditionKey.equals("200"))
   {
    while(S != null){
     System.out.println(S);
     fileData += S;
     S = inFromServer.readLine();
    }
    return true;
   }
   System.out.println("client is closed\n");
   clientSocket.close();
}
return false;
}

}