CODEWITHSUNDEEP
javasocketstcpnio
rms system
rms system

Reputation: 43

How much data was transferred?

When transmitting a file through socket in blocking mode

bytesTransferred = fileIChannel.transferTo(0, fileIChannel.size(), socketChannel);
// or using a buffer
ByteBuffer byteBuffer = ByteBuffer.allocateDirect(1024*8);
while (fileIChannel.read(byteBuffer) != -1) {
byteBuffer.flip();
bytesTransferred += socketChannel.write(byteBuffer);
byteBuffer.clear();

In the event of a connection failure, I need to keep the number of bytes transferred. I can do this by waiting for a response every from the server when it receives a particular number of bytes. Or, when the connection is restored, I send a request for the number of bytes received. Which of the options will be more correct? How is this problem usually resolved?

And the second question. Is data integrity guaranteed when sending large data through a socket?

Upvotes: 0

Views: 106

Answers (1)

user207421
user207421

Reputation: 310850

WIth this code you cannot tell. If you want to know that the peer application has received and processed sent data, the peer application has to tell you. TCP does buffering at both ends, so the API alone cannot tell you.

NB Your copy loop is wrong. It should be:

while ((fileIChannel.read(byteBuffer) != -1 && byteBuffer.position() > 0)
{
    byteBuffer.flip();
    bytesTransferred += socketChannel.write(byteBuffer);
    byteBuffer.compact();
}

and there should also be an error test on the write. At present you are assuming that everything got written to the SocketChannel on every write, which isn't guaranteed in non-blocking mode.

The code using transferTo() is also wrong, as transferTo() isn't guaranteed to perform the entire transfer: that's why it returns a count. You have to loop.

Upvotes: 1

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