无法使用Java中的套接字将文件从客户端发送到服务器_Java_File_Sockets_Network Programming_Client Server

无法使用Java中的套接字将文件从客户端发送到服务器

java file sockets network-programming

无法使用Java中的套接字将文件从客户端发送到服务器,java,file,sockets,network-programming,client-server,Java,File,Sockets,Network Programming,Client Server,我正在尝试编写一些代码，允许客户端将文件发送到服务器。但是我不能用这个代码发送文件服务器： package Server; import java.io.IOException; import java.net.ServerSocket; import java.net.Socket; public class SimpleServer { public static int serverThreadCount = 0; public static final int maxUser =

我正在尝试编写一些代码，允许客户端将文件发送到服务器。但是我不能用这个代码发送文件

服务器：

package Server;

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


public class SimpleServer {
public static int serverThreadCount = 0;
public static final int maxUser = 10;
public static String[] username = new String[maxUser];
public static String[] password = new String[maxUser];
public static String[] online = new String[maxUser];


public static void main(String[] args) {
    int id = 1;

    username[0] = "a";
    username[1] = "b";
    username[2] = "c";        
    username[3] = "d";
    username[4] = "e";
    username[5] = "f";
    username[6] = "g";
    username[7] = "h";
    username[8] = "i";
    username[9] = "j";

    for(int i=0; i<maxUser; i++)
    {
        password[i] = "123";
        online[i] = "free";
    }

    try
    {
        ServerSocket ss = new ServerSocket(7777);
        System.out.println("Server has successfully been started.");

        while(true) 
        {
            Socket socket = ss.accept();
            new Thread(new ServerThread(socket, id)).start();
            serverThreadCount++;
            System.out.println("Client " + id + " is now connected to the server.");
            id++;
        }
    }
    catch(IOException e)
    {
        System.err.println("IOException in serverSocket");
        e.printStackTrace();
    }
}

public static boolean verifyLogin(String u, String p)
{
    for(int i=0; i<maxUser; i++)
    {
        if(username[i].equals(u) && password[i].equals(p)) return true;
    }
    return false;
}

public static void setOnline(String name)
{
    for(int i=0; i<maxUser; i++)
    {
        if(online[i].equals("free")) 
        {
            online[i] = name;
            break;
        }
    }
}

public static boolean isOnline(String u)
{
    for(int i=0; i<maxUser; i++)
    {
        if(online[i].equals(u)) return true;
    }
    return false;
}
}

客户：

package Client;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.NoSuchElementException;
import java.util.Scanner;


public class SimpleClient {
    private static Socket socket;
    private static BufferedReader br;
    private static PrintWriter pw;
    private static String fileName;

public static void main(String[] args)
{
    Scanner scanner = new Scanner(System.in);
    String send = "", rec = "";

    try
    {
        socket = new Socket("localhost", 7777);

        br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        pw = new PrintWriter(socket.getOutputStream());
    }
    catch(UnknownHostException unknownHostException)
    {
        System.err.println("I don't know this" + socket.getPort() +"host!");
        unknownHostException.printStackTrace();
        System.exit(1);
    }
    catch(IOException e)
    {
        System.err.println("An IO exception has occured when initializing client.");
        closeconn();
        System.exit(1);
    }

    try
    {
        rec = br.readLine();
        if(rec != null)
        {
            System.out.println("Server: " + rec);
        }
        else
        {
            System.err.println("Cannot read from socket.");
            closeconn();
            System.exit(0);
        }
    }
    catch(IOException e)
    {
        System.err.println("Cannot read from socket.");
        closeconn();
        System.exit(0);
    }

    while(true)
    {
        System.out.println("Tell something to server:");
        try
        {
            send = scanner.nextLine();
            if(send.equals("sendfile"))
            {
                sendFile();
                break;
            }
        }
        catch(NoSuchElementException noSuchElementException)
        {
            noSuchElementException.printStackTrace();
        }
        catch(IllegalStateException illegalStateException)
        {
            illegalStateException.printStackTrace();
        }

        pw.println(send);
        pw.flush();

        try
        {
            rec = br.readLine();
            if(rec != null)
            {
                System.out.println("Server: " + rec);
            }
            else
            {
                System.err.println("Cannot read from socket.");
                break;
            }
        }
        catch(IOException e)
        {
            System.err.println("Cannot read from Socket");
            e.printStackTrace();
            break;
        }

        if(send.equals("BYE"))
        {
            System.out.println("See you later.");
            break;
        }
    }
    closeconn();
}

private static void closeconn()  {
    try
    {
        br.close();
        pw.close();
        socket.close();
    }
    catch(IOException e)
    {
        System.err.println("An error occured when closing client.");
        e.printStackTrace();
    }
}

private static String some()
{
    return "success!";
}

private static void sendFile()
{
    try
    {
        System.out.print("Please enter file name: ");
        fileName = br.readLine();

        File file = new File(fileName);
        byte[] bytearray = new byte[(int)file.length()];
        FileInputStream fis = new FileInputStream(file);
        BufferedInputStream bis = new BufferedInputStream(fis);

        DataInputStream dis = new DataInputStream(bis);
        dis.readFully(bytearray, 0, bytearray.length);

        OutputStream os = socket.getOutputStream();

        DataOutputStream dos = new DataOutputStream(os);
        dos.writeUTF(file.getName());
        dos.writeLong(bytearray.length);
        dos.write(bytearray, 0, bytearray.length);
        dos.flush();
        System.out.println("success!");
    }
    catch(FileNotFoundException fileNotFoundException)
    {
        System.err.println("File does not exist!");
        fileNotFoundException.printStackTrace();
    }
    catch(NullPointerException nullPointerException)
    {
        nullPointerException.printStackTrace();
    }        
    catch(EOFException eOFException)
    {
        System.err.println("End of file exception.");
        eOFException.printStackTrace();
    }
    catch(IOException iOException)
    {
        iOException.printStackTrace();
    }
}

public static void receiveFile(String fileName)
{
    try
    {
        int bytesRead;
        InputStream is = socket.getInputStream();

        DataInputStream dis = new DataInputStream(is);

        fileName = dis.readUTF();
        OutputStream os = new FileOutputStream("received_from_server_" + fileName);
        long size = dis.readLong();
        byte[] buffer = new byte[1024];
        while(size > 0 && (bytesRead = dis.read(buffer, 0, (int)Math.min(buffer.length, size))) != -1)
        {
            os.write(buffer, 0, bytesRead);
            size -= bytesRead;
        }
        os.close();
        is.close();
    }
    catch(IOException iOException)
    {
        iOException.printStackTrace();
    }
}
}

要登录，需要输入登录密码用户名

从客户端接收到“sendfile”后，类客户端调用sendfile方法，该方法将所需文件转换为字节数组。从客户端接收“sendfile”时，服务器调用接收并生成从客户端发送的文件的方法receiveFile

“我不能用此代码发送文件”是什么意思？您是否在服务器或客户端收到错误/异常，它是否在某个位置阻塞，在哪一点阻塞，您是否收到无效/不完整的数据等？@RolandBär，代码根本不起作用。没有例外或错误。在我将文件名输入到客户端后，它就保留在那里，什么也没有发生。这是什么意思？”fileName=br.readLine（）；'在客户端不返回？我想你在下一行尝试了一个断点，然后单步走了？

package Client;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.NoSuchElementException;
import java.util.Scanner;


public class SimpleClient {
    private static Socket socket;
    private static BufferedReader br;
    private static PrintWriter pw;
    private static String fileName;

public static void main(String[] args)
{
    Scanner scanner = new Scanner(System.in);
    String send = "", rec = "";

    try
    {
        socket = new Socket("localhost", 7777);

        br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        pw = new PrintWriter(socket.getOutputStream());
    }
    catch(UnknownHostException unknownHostException)
    {
        System.err.println("I don't know this" + socket.getPort() +"host!");
        unknownHostException.printStackTrace();
        System.exit(1);
    }
    catch(IOException e)
    {
        System.err.println("An IO exception has occured when initializing client.");
        closeconn();
        System.exit(1);
    }

    try
    {
        rec = br.readLine();
        if(rec != null)
        {
            System.out.println("Server: " + rec);
        }
        else
        {
            System.err.println("Cannot read from socket.");
            closeconn();
            System.exit(0);
        }
    }
    catch(IOException e)
    {
        System.err.println("Cannot read from socket.");
        closeconn();
        System.exit(0);
    }

    while(true)
    {
        System.out.println("Tell something to server:");
        try
        {
            send = scanner.nextLine();
            if(send.equals("sendfile"))
            {
                sendFile();
                break;
            }
        }
        catch(NoSuchElementException noSuchElementException)
        {
            noSuchElementException.printStackTrace();
        }
        catch(IllegalStateException illegalStateException)
        {
            illegalStateException.printStackTrace();
        }

        pw.println(send);
        pw.flush();

        try
        {
            rec = br.readLine();
            if(rec != null)
            {
                System.out.println("Server: " + rec);
            }
            else
            {
                System.err.println("Cannot read from socket.");
                break;
            }
        }
        catch(IOException e)
        {
            System.err.println("Cannot read from Socket");
            e.printStackTrace();
            break;
        }

        if(send.equals("BYE"))
        {
            System.out.println("See you later.");
            break;
        }
    }
    closeconn();
}

private static void closeconn()  {
    try
    {
        br.close();
        pw.close();
        socket.close();
    }
    catch(IOException e)
    {
        System.err.println("An error occured when closing client.");
        e.printStackTrace();
    }
}

private static String some()
{
    return "success!";
}

private static void sendFile()
{
    try
    {
        System.out.print("Please enter file name: ");
        fileName = br.readLine();

        File file = new File(fileName);
        byte[] bytearray = new byte[(int)file.length()];
        FileInputStream fis = new FileInputStream(file);
        BufferedInputStream bis = new BufferedInputStream(fis);

        DataInputStream dis = new DataInputStream(bis);
        dis.readFully(bytearray, 0, bytearray.length);

        OutputStream os = socket.getOutputStream();

        DataOutputStream dos = new DataOutputStream(os);
        dos.writeUTF(file.getName());
        dos.writeLong(bytearray.length);
        dos.write(bytearray, 0, bytearray.length);
        dos.flush();
        System.out.println("success!");
    }
    catch(FileNotFoundException fileNotFoundException)
    {
        System.err.println("File does not exist!");
        fileNotFoundException.printStackTrace();
    }
    catch(NullPointerException nullPointerException)
    {
        nullPointerException.printStackTrace();
    }        
    catch(EOFException eOFException)
    {
        System.err.println("End of file exception.");
        eOFException.printStackTrace();
    }
    catch(IOException iOException)
    {
        iOException.printStackTrace();
    }
}

public static void receiveFile(String fileName)
{
    try
    {
        int bytesRead;
        InputStream is = socket.getInputStream();

        DataInputStream dis = new DataInputStream(is);

        fileName = dis.readUTF();
        OutputStream os = new FileOutputStream("received_from_server_" + fileName);
        long size = dis.readLong();
        byte[] buffer = new byte[1024];
        while(size > 0 && (bytesRead = dis.read(buffer, 0, (int)Math.min(buffer.length, size))) != -1)
        {
            os.write(buffer, 0, bytesRead);
            size -= bytesRead;
        }
        os.close();
        is.close();
    }
    catch(IOException iOException)
    {
        iOException.printStackTrace();
    }
}
}