TcpClient read/write timeouts do not timeout

[Zytan]

I have a TcpClient. I set the read/write timeouts at 1 minute (in
milliseconds). I get a NetworkStream from it and confirm the timeouts
still exist. I do a NetworkStream.Write() and then a
NetworkStream.Read(). Sometimes it sits and waits -- on the Write()
or the Read() -- for 15 minutes before I get fed up and close the
app.....

I am not connecting to a TcpListener. I am connecting to a Socket
with ProtocolType.Tcp, which is acceptable. These read/writes
normally work, but when I get 3 or 4 TcpClients all connecting at the
same time, connection problems start. I don't understand why some of
the connections fail. And, when they do fail, why don't the timeouts
work?

I believe I have a bug in the server, but still, the timeouts should
timeout.

[Peter Duniho]

On Mon, 21 Jul 2008 08:11:48 -0700, Zytan <zy**********@gmail.comwrote:

[...]
I believe I have a bug in the server, but still, the timeouts should
timeout.

Hard to say without seeing an actual concise-but-complete code example.
That said, your description isn't all that clear either. Are you having
read/write problems or connection problems? One paragraph says the
former, while another says the latter.

Beware of using the TCP timeout: once the timeout occurs, the socket is no
longer usable. Depending on your intent, you may be better off
implementing timeout logic yourself elsewhere.

Pete

[Zytan]

(It appears my reply isn't appearing, so I'll write again:)

Hard to say without seeing an actual concise-but-complete code example.

I use the code from this example:
http://msdn.microsoft.com/en-us/libr...tcpclient.aspx
(except I implement timeouts.)

Are you having
read/write problems or connection problems?

It connects fine. The server sees the connection. The client gets
stuck in the stream.Write() call, and the server never sees any data
from it. (This occurs 1% o the time. The other 99%, everything works
fine.)

Beware of using the TCP timeout: once the timeout occurs, the socket is no
longer usable.

Ok.

Depending on your intent, you may be better off
implementing timeout logic yourself elsewhere.

The implementation is: 1. connect, 2. send data, 3. get reply, 4.
disconnect, so TcpClient seemed like the answer, since it was
synchronous, just as I wanted it to be, to avoid the hassle of
asynchronous code.

I even TURNED THE SERVER OFF once the stream.Write() got hung up, to
see if that would end the stream.Write() call... and it doesn't.
Write() should end because there's NO server and because the timeout
is 1 minute, and it's been 20 minutes now. Even if my server code is
a mess of bugs, this makes no sense.
Thanks, Pete,

Zytan

[Zytan]

I guess I've conclusively shown that either .NET is fried, or
something else is causing this issue (i.e. me). And I think I may
have found it.... so, hold up... before you waste your time reading my
replies........

Zytan

[Zytan]

I guess I've conclusively shown that either .NET is fried, or

something else is causing this issue (i.e. me). And I think I may
have found it.... so, hold up... before you waste your time reading my
replies........

I am SO STUPID...

My log files that supposedly were pinning the issue down to the
stream.Write() line, which was supposedly hanging up, actually pinned
it down to two functions... the Write() call AND an encryption
function made my yours truly, which was entering an INFINITE LOOP...
yeah, really.

So my first mistake was not testing my encryption function.
My second mistake was that the log files didn't pin down the EXACT
line of code of the error. How I did this, I don't know.

Sorry for wasting your time.

Zytan

[Peter Duniho]

On Mon, 21 Jul 2008 10:31:42 -0700, Zytan <zy**********@gmail.comwrote:

[...]
My log files that supposedly were pinning the issue down to the
stream.Write() line, which was supposedly hanging up, actually pinned
it down to two functions... the Write() call AND an encryption
function made my yours truly, which was entering an INFINITE LOOP...
yeah, really.

I'm glad you were able to find the issue. Not to belabor the point,
but...had you posted a concise-but-complete code sample that demonstrated
the problem, the above may well have been noted by someone else (possibly
even me :) ), leading to a quicker solution.

In other words, this is exactly why it's so important to post actual,
real-world code. Without the code, no one can say what's wrong, nor even
confirm that _your_ code is correct.

Pete

[Zytan]

I'm glad you were able to find the issue. Not to belabor the point,

but...had you posted a concise-but-complete code sample that demonstrated
the problem, the above may well have been noted by someone else (possibly
even me :) ), leading to a quicker solution.

No, belabor away, you're completely right.

I posted in the hopes of wondering if someone could uncover any
gotchas about TcpClient. I was just being stupid. As soon as it
didn't return after the timeout, I should have known that something
else was causing the delay.

And yes, if I posted even a small snippet of code, you would have
asked me WTF is that encryption function doing, and I would have said
"aha"...

Zytan

[Zytan]

......an encryption

function made my yours truly, which was entering an INFINITE LOOP...

The bug was operator precedence, I had something like:
x << 1 + 1
assuming it would do:
(x << 1) + 1
but in fact, it does:
x << (1 + 1)

VC++ warns about this, because I do this ALL the time, since I assume
<< and >are multiplication and division in my head, which comes
first. C# does not give any warning.

Zytan

[Peter Duniho]

On Mon, 21 Jul 2008 11:19:17 -0700, Zytan <zy**********@gmail.comwrote:

>......an encryption
function made my yours truly, which was entering an INFINITE LOOP...

The bug was operator precedence, I had something like:
x << 1 + 1
assuming it would do:
(x << 1) + 1
but in fact, it does:
x << (1 + 1)

VC++ warns about this, because I do this ALL the time, since I assume
<< and >are multiplication and division in my head, which comes
first. C# does not give any warning.

For what it's worth, if "in your head" you are using the shift operators
as division and multiplication, you should use division and multiplication
operators instead.

Being careful about operator precedence is obviously important in any
case, but in this particular situation, using actual multiplication or
division operators may well have avoided the bug, as well as made the code
more clear as to the intent.

Either way, it's the mixing of math and bit-twiddling that was your
problem. The "+ 1" (as opposed to "| 1") suggests this is more about math
than bit-twiddling, which would mean it's a multiplication disguised as a
shift operation. But even if you really should have been using << with |
(i.e. it's bit-twiddling) you wouldn't have had the bug had you used the
correct operators together, since the << operator _does_ have higher
precedence than the | operator.

Of course, never any harm in providing explicit precedence via
parentheses. But I still think it's better to use math operators for math
and bit-twiddling operators for bit-twiddling. :)

Pete

[Zytan]

For what it's worth, if "in your head" you are using the shift operators

as division and multiplication, you should use division and multiplication
operators instead.

Right.

Being careful about operator precedence is obviously important in any
case, but in this particular situation, using actual multiplication or
division operators may well have avoided the bug, as well as made the code
more clear as to the intent.

Yup.

Either way, it's the mixing of math and bit-twiddling that was your
problem. The "+ 1" (as opposed to "| 1") suggests this is more about math
than bit-twiddling, which would mean it's a multiplication disguised as a
shift operation. But even if you really should have been using << with |
(i.e. it's bit-twiddling) you wouldn't have had the bug had you used the
correct operators together, since the << operator _does_ have higher
precedence than the | operator.

Ah.

I was doing bit-twiddling, and not math. So, I should be using <<
with |, just like you say.

I know I'm not the only one who got hit with mixing << and +, though,
since VC++ has a warning about it. But, this doesn't negate all the
great points you've made.

Of course, never any harm in providing explicit precedence via
parentheses.

Right, I find myself doing this a lot. Why didn't I this time?
Probably tired and pressured for time.

But I still think it's better to use math operators for math
and bit-twiddling operators for bit-twiddling. :)

Of course. I had never before thought about +1 and |1 as being any
different when the 1st bit is known to be cleared... but it makes
perfect sense to think about it in the way you mention....

Great tips! I'm glad I reported the bug now.

Zytan

[Peter Duniho]

On Mon, 21 Jul 2008 12:11:17 -0700, Zytan <zy**********@gmail.comwrote:

[...]
Great tips! I'm glad I reported the bug now.

Glad to help. As the saying goes, I learn far more from my mistakes than
from my successes. I feel like I know a lot, so you can only imagine how
many mistakes it took to get to this point. And I intend to make a LOT
more mistakes before I'm done. Otherwise, how will I learn. :)

Pete