java 使用java套接字将文本文件从客户端发送到服务器

Sending a text file from client to server using java sockets

提问by user1081326

This is an assignment.

这是一个任务。

Im looking for a bit of advice as to where i am going wrong here. My aim is to read text from a file, send it to the server and write that text into a new file.

我正在寻找一些关于我在这里出错的地方的建议。我的目标是从文件中读取文本，将其发送到服务器并将该文本写入一个新文件。

Problem being im not exactly sure how to do it, I have looked at many examples none of which being much help.

问题是我不确定该怎么做，我看过很多例子，但没有一个有多大帮助。

To explain the program as is. The user would be asked to input a code which relates to an if statemnt of that code. The one i want to focus on is code 200 which is the upload file to server code.

按原样解释程序。将要求用户输入与该代码的 if 语句相关的代码。我想关注的是代码 200，它是上传文件到服务器的代码。

When i run the code i have i get this error below. Could someone explain to me where i am going wrong, I'd appreciate it.

当我运行代码时，我在下面收到此错误。有人可以向我解释我哪里出错了，我会很感激。

    Connection request made
Enter Code: 100 = Login, 200 = Upload, 400 = Logout:
200
java.net.SocketException: Connection reset
        at java.net.SocketInputStream.read(Unknown Source)
        at java.net.SocketInputStream.read(Unknown Source)
        at sun.nio.cs.StreamDecoder.readBytes(Unknown Source)
        at sun.nio.cs.StreamDecoder.implRead(Unknown Source)
        at sun.nio.cs.StreamDecoder.read(Unknown Source)
        at java.io.InputStreamReader.read(Unknown Source)
        at java.io.BufferedReader.fill(Unknown Source)
        at java.io.BufferedReader.readLine(Unknown Source)
        at java.io.BufferedReader.readLine(Unknown Source)
        at MyStreamSocket.receiveMessage(MyStreamSocket.java:50)
        at EchoClientHelper2.getEcho(EchoClientHelper2.java:34)
        at EchoClient2.main(EchoClient2.java:99)

And this error on the server:

服务器上的这个错误：

    Waiting for a connection.
connection accepted
message received: 200
java.net.SocketException: Socket is not connected
        at java.net.Socket.getInputStream(Unknown Source)
        at EchoServer2.main(EchoServer2.java:71)

回答by Simon G.

Your MyStreamSocketclass does not need to extend Socket. The mysterious error message is because the Socket represented by MyStreamSocket is never connected to anything. The Socket referenced by its socketmember is the one that is connected. Hence when you get the input stream from MyStreamSocket it genuinely is not connected. That causes an error, which means the client shuts down. That causes the socket to close, which the server duly reports

您的MyStreamSocket类不需要扩展 Socket。神秘的错误信息是因为 MyStreamSocket 代表的 Socket 从未连接到任何东西。其socket成员引用的 Socket是连接的那个。因此，当您从 MyStreamSocket 获取输入流时，它确实没有连接。这会导致错误，这意味着客户端关闭。这会导致套接字关闭，服务器会及时报告

The use of BufferedReader is going to cause you problems. It always reads as much as it can into its buffer, so at the start of a file transfer it will read the "200" message and then the first few Kb of the file being sent which will get parsed as character data. The result will be a whole heap of bugs.

BufferedReader 的使用会给你带来问题。它总是尽可能多地读取缓冲区，因此在文件传输开始时，它将读取“200”消息，然后读取正在发送的文件的前几 Kb，这将被解析为字符数据。结果将是一大堆错误。

I suggest you get rid of BufferedReader right now and use DataInputStream and DataOutputStream instead. You can use the writeUTF and readUTF methods to send your textual commands. To send the file I would suggest a simple chunk encoding.

我建议你现在摆脱 BufferedReader 并使用 DataInputStream 和 DataOutputStream 代替。您可以使用 writeUTF 和 readUTF 方法发送文本命令。要发送文件，我建议使用简单的块编码。

It's probably easiest if I give you code.

如果我给你代码，这可能是最简单的。

First your client class.

首先是您的客户课程。

import java.io.*;
import java.net.InetAddress;

public class EchoClient2 {

    public static void main(String[] args) {
        InputStreamReader is = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(is);

        File file = new File("C:\MyFile.txt");

        try {
            System.out.println("Welcome to the Echo client.\n"
                    + "What is the name of the server host?");
            String hostName = br.readLine();
            if( hostName.length() == 0 ) // if user did not enter a name
                hostName = "localhost"; // use the default host name
            System.out.println("What is the port number of the server host?");
            String portNum = br.readLine();
            if( portNum.length() == 0 ) portNum = "7"; // default port number
            MyStreamSocket socket = new MyStreamSocket(
                    InetAddress.getByName(hostName), Integer.parseInt(portNum));
            boolean done = false;
            String echo;
            while( !done ) {

                System.out.println("Enter Code: 100 = Login, 200 = Upload, 400 = Logout: ");
                String message = br.readLine();
                boolean messageOK = false;

                if( message.equals("100") ) {
                    messageOK = true;
                    System.out.println("Enter T-Number: (Use Uppercase 'T')");
                    String login = br.readLine();
                    if( login.charAt(0) == 'T' ) {
                        System.out.println("Login Worked fantastically");
                    } else {
                        System.out.println("Login Failed");
                    }
                    socket.sendMessage("100");
                }

                if( message.equals("200") ) {
                    messageOK = true;
                    socket.sendMessage("200");
                    socket.sendFile(file);
                }
                if( (message.trim()).equals("400") ) {
                    messageOK = true;
                    System.out.println("Logged Out");
                    done = true;
                    socket.sendMessage("400");
                    socket.close();
                    break;
                }

                if( ! messageOK ) {
                    System.out.println("Invalid input");
                    continue;
                }

                // get reply from server
                echo = socket.receiveMessage();
                System.out.println(echo);
            } // end while
        } // end try
        catch (Exception ex) {
            ex.printStackTrace();
        } // end catch
    } // end main
} // end class

Then your server class:

然后你的服务器类：

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

public class EchoServer2 {
    static final String loginMessage = "Logged In";

    static final String logoutMessage = "Logged Out";


    public static void main(String[] args) {
        int serverPort = 7; // default port
        String message;

        if( args.length == 1 ) serverPort = Integer.parseInt(args[0]);
        try {
            // instantiates a stream socket for accepting
            // connections
            ServerSocket myConnectionSocket = new ServerSocket(serverPort);
            /**/System.out.println("Daytime server ready.");
            while( true ) { // forever loop
                // wait to accept a connection
                /**/System.out.println("Waiting for a connection.");
                MyStreamSocket myDataSocket = new MyStreamSocket(
                        myConnectionSocket.accept());
                /**/System.out.println("connection accepted");
                boolean done = false;
                while( !done ) {
                    message = myDataSocket.receiveMessage();

                    /**/System.out.println("message received: " + message);

                    if( (message.trim()).equals("400") ) {
                        // Session over; close the data socket.
                        myDataSocket.sendMessage(logoutMessage);
                        myDataSocket.close();
                        done = true;
                    } // end if

                    if( (message.trim()).equals("100") ) {
                        // Login
                        /**/myDataSocket.sendMessage(loginMessage);
                    } // end if

                    if( (message.trim()).equals("200") ) {

                        File outFile = new File("C:\OutFileServer.txt");
                        myDataSocket.receiveFile(outFile);
                        myDataSocket.sendMessage("File received "+outFile.length()+" bytes");
                    }

                } // end while !done
            } // end while forever
        } // end try
        catch (Exception ex) {
            ex.printStackTrace();
        }
    } // end main
} // end class

Then the StreamSocket class:

然后是 StreamSocket 类：

public class MyStreamSocket {
    private Socket socket;

    private DataInputStream input;

    private DataOutputStream output;


    MyStreamSocket(InetAddress acceptorHost, int acceptorPort)
            throws SocketException, IOException {
        socket = new Socket(acceptorHost, acceptorPort);
        setStreams();
    }


    MyStreamSocket(Socket socket) throws IOException {
        this.socket = socket;
        setStreams();
    }


    private void setStreams() throws IOException {
        // get an input stream for reading from the data socket
        input = new DataInputStream(socket.getInputStream());
        output = new DataOutputStream(socket.getOutputStream());
    }


    public void sendMessage(String message) throws IOException {
        output.writeUTF(message);
        output.flush();
    } // end sendMessage


    public String receiveMessage() throws IOException {
        String message = input.readUTF();
        return message;
    } // end receiveMessage


    public void close() throws IOException {
        socket.close();
    }


    public void sendFile(File file) throws IOException {
        FileInputStream fileIn = new FileInputStream(file);
        byte[] buf = new byte[Short.MAX_VALUE];
        int bytesRead;        
        while( (bytesRead = fileIn.read(buf)) != -1 ) {
            output.writeShort(bytesRead);
            output.write(buf,0,bytesRead);
        }
        output.writeShort(-1);
        fileIn.close();
    }



    public void receiveFile(File file) throws IOException {
        FileOutputStream fileOut = new FileOutputStream(file);
        byte[] buf = new byte[Short.MAX_VALUE];
        int bytesSent;        
        while( (bytesSent = input.readShort()) != -1 ) {
            input.readFully(buf,0,bytesSent);
            fileOut.write(buf,0,bytesSent);
        }
        fileOut.close();
    }    
} // end class

Ditch the "helper" class. It is not helping you.

抛弃“助手”类。它没有帮助你。