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Timeout Exceptions and the state of DataInputStream

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  Timeout Exceptions and the state of DataInputStream Ivan Ryan <ivan.ryan@gmail.com> - 2012-03-28 16:59 -0700
    Re: Timeout Exceptions and the state of DataInputStream Knute Johnson <nospam@knutejohnson.com> - 2012-04-02 14:14 -0700
    Re: Timeout Exceptions and the state of DataInputStream Arne Vajhøj <arne@vajhoej.dk> - 2012-04-02 19:40 -0400

#13305 — Timeout Exceptions and the state of DataInputStream

I was wondering how the DataInputStream class handles Socket timeouts.

For example, with code like the following:

someSocket.setSoTimeout(1000);

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

long x = in.readLong()

What would happen if the stream times out when reading the long.
Would calling in.readLong() again give the correct value.  This
assumes that the socket doesn't timeout the 2nd time.

I assume that since the DataInputStream could be reading one byte at a
time, it doesn't hold internal state.  This would mean that a few
bytes of the long could be lost?

Another option is that the stream would "unread" the bytes or
something.

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#13319

On 3/28/2012 4:59 PM, Ivan Ryan wrote:
> I was wondering how the DataInputStream class handles Socket timeouts.
>
> For example, with code like the following:
>
> someSocket.setSoTimeout(1000);
>
> DataInputStream in = new DataInputStream(someSocket.getInputStream());
>
> long x = in.readLong()
>
> What would happen if the stream times out when reading the long.
> Would calling in.readLong() again give the correct value.  This
> assumes that the socket doesn't timeout the 2nd time.
>
> I assume that since the DataInputStream could be reading one byte at a
> time, it doesn't hold internal state.  This would mean that a few
> bytes of the long could be lost?
>
> Another option is that the stream would "unread" the bytes or
> something.

I'm not sure why you would have a timeout of only 1 second but I would 
not expect the socket to timeout if you were actually reading data. 
Timeouts are typically designed to detect a lack of transmission of data 
for a given period.  For a system with a remote connection I would think 
that 1 second could easily be too short a period.

-- 

Knute Johnson

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#13327

On 3/28/2012 7:59 PM, Ivan Ryan wrote:
> I was wondering how the DataInputStream class handles Socket timeouts.
>
> For example, with code like the following:
>
> someSocket.setSoTimeout(1000);
>
> DataInputStream in = new DataInputStream(someSocket.getInputStream());
>
> long x = in.readLong()
>
> What would happen if the stream times out when reading the long.

I think DataInputStream should just pass the SocketTimeoutException
on from the some InputStream.

> Would calling in.readLong() again give the correct value.  This
> assumes that the socket doesn't timeout the 2nd time.
>
> I assume that since the DataInputStream could be reading one byte at a
> time, it doesn't hold internal state.  This would mean that a few
> bytes of the long could be lost?
>
> Another option is that the stream would "unread" the bytes or
> something.

Unless the Java docs actually guarantees a specific behavior, then
you should not assume anything about lost or non lost. Anything could
happen and it could differ between implementation and between version.

You may need to redesign the logic.

Arne

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