数据不会在QTcpSockets和Java Sockets之间传输

Question

所以我有两个应用程序，一个是使用Qt5用C++编写的，另一个是用Java语言编写的。C++应用程序充当连接到java应用程序中的ServerSocket对象的客户端，然后java应用程序从该连接实例化一个套接字。然后，当我尝试向服务器发送字符串时，要么必须重复发送字符串(比如20000次)，要么服务器什么也收不到。

QString s = " This is a test string that will be sent to the server upon connection\n";
QTcpSocket *sock = new QTcpSocket;
sock->connectToHost(QHostAddress::LocalHost, 5000, QIODevice::ReadWrite);
sock->waitForConnected(5000);
QTextStream out(sock);
while(!sock->waitForBytesWritten(3000)) {
        out << s << endl;
}

在上面的代码不会产生任何结果的情况下，下面的代码会产生分段的字符串以及服务器的重复接收字符串：

QString s = " This is a test string that will be sent to the server upon connection\n";
QTcpSocket *sock = new QTcpSocket;
sock->connectToHost(QHostAddress::LocalHost, 5000, QIODevice::ReadWrite);
sock->waitForConnected(5000);
QTextStream out(sock);
do {
        out << s << endl;
} while(!sock->waitForBytesWritten(3000) | 1);

服务器是一个简单的java程序，如下所示：

ServerSocket ss = new ServerSocket(5000);
Socket s = ss.accept();
DataInputStream in = new DataInputStream(s.getInputStream());
while (true){
        String tmp = in.readUTF();
        System.out.println(tmp);
        if (tmp.contains(" ")){
              break;
}

我希望输出是一个简单的This is a test string that will be sent to the server upon connection；然而，结果要么是什么都没有，要么是以下内容：

his is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

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 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

 This is a test string that will be sent to the server upon connection

你知道我该如何解决这个问题吗？

Answer 1

因此，解决方案是将数据读取到byte[]中，然后使用字符串构造函数将其转换为字符串，如下所示：

ServerSocket ss = new ServerSocket(5000);

Socket s = ss.accept();

DataInputStream in = new DataInputStream(s.getInputStream());

byte[] b = new byte[1024];
in.read(b);

String tmp = new String(b, "UTF8");
System.out.println(b);
System.out.println(tmp);

我不知道为什么，但这是我得出的解决方案。客户端几乎保持不变，尽管做了一些细微的改变：

QString s = "This is a test string that will be sent to the server upon connection\n";

QTcpSocket *sock = new QTcpSocket;

sock->connectToHost(QHostAddress::LocalHost, 5000, QIODevice::ReadWrite);

sock->waitForConnected(5000);


do {
        sock->write(s.toUtf8());
        sock->flush();

        sock->waitForBytesWritten();
} while (sock->isValid() && sock->bytesToWrite() > 0);

Answer 2

(1)在Windows上waitForBytesWritten可能失败-最好使用信号bytesWritten()

(2)循环

while(!sock->waitForBytesWritten(3000) | 1);

在我看来，这是一个无穷无尽的循环，独立于waitForBytesWritten的返回代码

(3)在您的程序环境中，waitForBytesWritten的概念是什么？它可能会在写入流的第一个字节之后返回！

(4)你的想法是什么？

if (tmp.contains(" ")){
              break;

对我来说，这看起来可能会在收到任何空格后中断-例如，" this“之后的第一个空格。它可能会在几行之后中断，这取决于readUTF提供了多少(我不是Java专家)。

(5) readUTF期望使用修改后的UTF8格式的字符串，但Qt不会发送修改后的UTF8格式的字符串(包含长度的前导16位整数)。因此，Java会将前两个字符('Th')解释为长度，然后彩票可能会开始-根据这两个字符，解码将返回看似任意的结果。