Java 字节流。读取操作有时不读取写入的内容

Question

我正在尝试实现一个具有自动重复请求策略的通信系统。我用了三个类：Transmitter，Channel，Receiver。我有消息的最大字节数 (window)。但是当我收到发送的字节时，有时我收到的字节数少于window。为什么？我的代码是这样的：

传送器

int n = 0;
int remaining, length;
while (n<channelBytes.length) {
     remaining = channelBytes.length-n;
     length = (remaining<window)? remaining : window;
     outputStream.write(channelBytes,n,length);
     // wait for the ack
     byte[] b = new byte[4];
     channel.socket().setSoTimeout(2000);
     inputStream.read(b);
     n += ByteBuffer.wrap(b).getInt();
}

频道

bytes = new byte[SystemModel.WINDOW];
while(true) {
    // receive from Tx
    upInputStream.read(bytes);
    // insert channel error
    insertError(bytes);
    Thread.sleep(propagationDelay + transmissionDelay);
    // send bytes to Rx
    downOutputStream.write(bytes);
    // wait for the ack from Rx
    clientChannelDown.socket().setSoTimeout(2000);
    byte[] ack = new byte[4];
    downInputStream.read(ack);
    // send ack to Tx
    upOutputStream.write(ByteBuffer.allocate(4).put(ack).array());
}

接收者

byte[] b = new byte[SystemModel.WINDOW];
while (true) {
    try {
        int received = inputStream.read(b);
        channelCoding.decodePartially(b);                                        
    }catch (SocketTimeoutException te){  
        break;
    } catch (IOException e) {
        e.printStackTrace();
    } catch (DataFormatException e) {
        // send ack
        int ack = Integer.parseInt(e.getMessage());
        try {
            outputStream.write(ByteBuffer.allocate(4).putInt(ack).array());
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }
}

在接收器中，字节数组 "b" 并不总是 window 的长度。

Answer 1

无效代码。请参阅 Java 文档。 InputStream.read(byte[] [,...]) 没有义务传输超过一个字节，并且在不将结果存储到变量中的情况下调用它是永远无效的。如果您期望超过一个字节，则必须循环或使用 DataInputStream.readFully().

在Java中复制流的规范方式如下：

while ((count = in.read(buffer)) > 0)
{
    out.write(buffer, 0, count);
}

对于ByteBuffers和Channels的情况如下：

while (in.read(buffer) > 0 || buffer.position() > 0)
{
    buffer.flip();
    out.write(buffer);
    buffer.compact();
}

如果您编码正确，则无需将睡眠插入网络代码。

E&OE

Java 字节流。读取操作有时不读取写入的内容

Java stream of byte. Read operation sometimes doesn't read what was written

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byte

inputstream

outputstream

stream