public class PipeDataReceiver extends AbstractLoggingBean implements ChannelDataReceiver
ChannelDataReceiver
that buffers the received data into byte buffer and provides an InputStream
to
consume them.log
Constructor and Description |
---|
PipeDataReceiver(PropertyResolver resolver,
LocalWindow localWindow) |
Modifier and Type | Method and Description |
---|---|
void |
close() |
int |
data(ChannelSession channel,
byte[] buf,
int start,
int len)
Called when the server receives additional bytes from the client.
|
InputStream |
getIn() |
public PipeDataReceiver(PropertyResolver resolver, LocalWindow localWindow)
public InputStream getIn()
public void close() throws IOException
close
in interface Closeable
close
in interface AutoCloseable
IOException
public int data(ChannelSession channel, byte[] buf, int start, int len) throws IOException
ChannelDataReceiver
Called when the server receives additional bytes from the client. When Closeable.close()
-d then indicates EOF -
The client will no longer send us any more data.
SSH channels use the windowing mechanism to perform flow control, much like TCP does. The server gives the client the initial window size, which represents the number of bytes the client can send to the server. As the server receives data, it can send a message to the client to allow it to send more data.
The return value from this method is used to control this behaviour. Intuitively speaking, the callee returns the number of bytes consumed by this method, by the time this method returns. Picture a one-way long bridge (for example Golden Gate Bridge) with toll plazas on both sides. The window size is the maximum number of cars allowed on the bridge. Here we are on the receiving end, so our job here is to count the number of cars as it leaves the bridge, and if enough of them left, we'll signal the sending end that they can let in more cars. The return value of this method counts the number of cars that are leaving in this batch.
In simple cases, where the callee has consumed the bytes before it returns, the return value must be the same value as the 'len' parameter given.
On the other hand, if the callee is queueing up the received bytes somewhere to be consumed later (for example by
another thread), then this method should return 0, for the bytes aren't really consumed yet. And when at some
later point the bytes are actually used, then you'll invoke channel.getLocalWindow().consumeAndCheck(len)
to let the channel know that bytes are consumed.
This behaviour will result in a better flow control, as the server will not allow the SSH client to overflow its buffer. If instead you always return the value passed in the 'len' parameter, the place where you are queueing up bytes may overflow.
In either case, the callee must account for every bytes it receives in this method. Returning 0 and failing to
call back channel.getLocalWindow().consumeAndCheck(len)
later will dry up the window size, and eventually
the client will stop sending you any data.
In the SSH protocol, this method invocation is triggered by a SSH_MSG_CHANNEL_DATA message.
data
in interface ChannelDataReceiver
channel
- The caller to which this ChannelDataReceiver
is assigned. Never null.buf
- Holds the bytes received. This buffer belongs to the caller, and it might get reused by the
caller as soon as this method returns.start
- buf[start] is the first byte that received from the client.len
- the length of the bytes received. Can be zero.IOException
- if failed to consume the dataCopyright © 2008–2024 The Apache Software Foundation. All rights reserved.