java - 通过Java套接字发送多个文件

Question

我试图让一个程序正常工作，在该程序中客户端将同一文件发送到服务器100次，然后检查以确保所有100个文件与原始文件相同。现在，我无法使它正常工作，因为服务器从客户端读取了任意数量的字节，这导致某些文件中的字节过多，我不确定如何继续。现在，它将正确发送所有100个文件，但其中一些文件中包含太多内容。
客户代码

String sentence;
    InetAddress host = InetAddress.getLocalHost();
    Socket clientSocket = new Socket(host, 6789);
    DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());

    long startTime, endTime, tGap, totalTime;
    byte[] sendData;
    int filesSent = 0;

    File fs = new File("Test1.txt");

    int fileLength = (int) fs.length();
    totalTime = 0;

    while (filesSent < 100) {
        FileInputStream fin = new FileInputStream(fs);
        int numBytes = 0;
        System.out.println("Sending file to server...");
        sendData = new byte[1024];
        if (fileLength < 1024) {
            numBytes = fin.read(sendData, 0, fileLength);
        } else {
            numBytes = fin.read(sendData, 0, 1024);
        }

        startTime = System.currentTimeMillis();
        int count = 0;
        while (numBytes != -1) {
            count += numBytes;
            System.out.println(numBytes);
            sentence = new String(sendData);
            outToServer.writeBytes(sentence);
            numBytes = fin.read(sendData, 0, 1024);
        }
        System.out.println(count);
        endTime = System.currentTimeMillis();
        tGap = endTime - startTime;
        totalTime = totalTime + tGap;
        System.out.println("Finished run " + filesSent + " with a time of " + tGap);
        filesSent++;
        fin.close();
        outToServer.flush();
    }
    clientSocket.close();

    System.out.println("I am done to send " + filesSent + " times file, and the average time is: " + (double) totalTime / filesSent);
}

服务器代码

String clientSentence;
    int filesRecieved = 0;
    ServerSocket welcomeSocket = new ServerSocket(6789);
    int numError = 0;
    int numBytes;
    char check = 'a';
    System.out.println("I am starting now....");

    long startTime, endTime, tGap, totalTime;
    totalTime = 0;

    Socket connectionSocket;
    connectionSocket = welcomeSocket.accept();
    BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));

    while(filesRecieved < 100) {
        FileOutputStream outPut = new FileOutputStream("receivedFile" + filesRecieved + ".txt");
        char[] receiveData = new char[1024];
        numBytes = inFromClient.read(receiveData, 0, 1024);
        while(numBytes != 1024){
            numBytes += inFromClient.read(receiveData,0,1024-numBytes);
        }
        System.out.println("OG Bytes:" + numBytes);
        startTime = System.currentTimeMillis();

        int count = 0;
        while (numBytes != -1 && count < 105942) {
            try {
                count += numBytes;
                clientSentence = new String(receiveData, 0, numBytes);
                outPut.write(clientSentence.getBytes(), 0, numBytes);
                System.out.println(numBytes);
                numBytes = inFromClient.read(receiveData, 0, 1024);
                System.out.println(count);
            }catch(Exception e){
                break;
            }
        }
        outPut.close();
        endTime = System.currentTimeMillis();
        tGap = endTime - startTime;
        totalTime = totalTime + tGap;
        System.out.println("I have received" + "receivedFile" + filesRecieved + ".txt using time = " + tGap);
        filesRecieved++;
    }

    connectionSocket.close();

    System.out.println("I am done now..." + "and the average time used to receive each copy is: " + totalTime / filesRecieved);
    welcomeSocket.close();

Answer 1

TCP是字节流。它没有消息的概念。因此，您需要以一种这样的方式对文件数据进行构图，以使接收方知道一个文件在哪里结束而下一个文件在哪里开始。在这种情况下，您需要先发送文件大小，然后再发送文件数据，这样接收方才能知道每个文件有多少字节。
另外，您没有适当注意每次调用read()告诉您实际上已读取的字节数。您为它提供了很大的缓冲区，但是不能保证整个缓冲区都会被填满。特别是在文件末尾。
并且不要使用字符串传输二进制文件数据!
尝试类似这样的方法:
客户:

File fs = new File("Test1.txt");
long fileLength = fs.length();

InetAddress host = InetAddress.getLocalHost();
Socket clientSocket = new Socket(host, 6789);
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());

long startTime, endTime, tGap, totalTime = 0;
byte[] sendData = new byte[1024];
int numBytes, filesSent = 0;

while (filesSent < 100) {
    FileInputStream fin = new FileInputStream(fs);
    long thisFileLength = fileLength;

    System.out.println("Sending file to server...");
    startTime = System.currentTimeMillis();

    outToServer.writeLong(thisFileLength);

    while (thisFileLength > 0) {
        if (thisFileLength < sendData.length) {
            numBytes = fin.read(sendData, 0, (int) thisFileLength);
        } else {
            numBytes = fin.read(sendData, 0, sendData.length);
        }

        System.out.println(numBytes);
        if (numBytes < 1) {
            break;
        }

        outToServer.write(sendData, 0, numBytes);
        thisFileLength -= numBytes;
    }

    outToServer.flush();

    endTime = System.currentTimeMillis();
    tGap = endTime - startTime;
    totalTime = totalTime + tGap;
    System.out.println("Finished run " + filesSent + " with a time of " + tGap);
    filesSent++;

    fin.close();

    if (thisFileLength > 0) {
        break;
    }
}

clientSocket.close();

System.out.println("I am done to send " + filesSent + " times file, and the average time is: " + (double) totalTime / filesSent);

服务器:

ServerSocket welcomeSocket = new ServerSocket(6789);
System.out.println("I am starting now....");

Socket connectionSocket;
connectionSocket = welcomeSocket.accept();
DataInputStream inFromClient = new DataInputStream(new BufferedInputStream(connectionSocket.getInputStream()));

long startTime, endTime, tGap, totalTime = 0;
byte[] receiveData = new byte[1024];
int numBytes, filesRecieved = 0;

while (filesRecieved < 100) {
    string filename = "receivedFile" + filesRecieved + ".txt";
    FileOutputStream outPut = new FileOutputStream(filename);

    startTime = System.currentTimeMillis();

    long fileLength = inFromClient.readLong();
    System.out.println("OG Bytes: " + fileLength);

    while (fileLength > 0) {
        if (fileLength < receiveData.length) {
            numBytes = inFromClient.read(receiveData, 0, (int) fileLength);
        }
        else {
            numBytes = inFromClient.read(receiveData, 0, receiveData.length);
        }

        if (numBytes < 1) {
            break;
        }

        try {
            outPut.write(receiveData, 0, numBytes);
            System.out.println(numBytes);
        }
        catch (Exception e) {
            break;
        }

        fileLength -= numBytes;
    }

    outPut.close();

    endTime = System.currentTimeMillis();
    tGap = endTime - startTime;
    totalTime = totalTime + tGap;
    System.out.println("I have received " + filename + " using time = " + tGap);
    filesRecieved++;

    if (fileLength > 0) {
        break;
    }
}

connectionSocket.close();

System.out.println("I am done now... and the average time used to receive each copy is: " + totalTime / filesRecieved);
welcomeSocket.close();