How do you set a timeout on BufferedReader and PrintWriter in Java 1.4?
Solution 1
Since calling socket.close() did not seem to interrupt the block at br.readLine(), I did a little workaround. When disconnecting the client from the server, I merely send through a string "bye", and told the server to close the socket connection when it receives this command.
while ((str = br.readLine()) != null){
// If we receive a command of "bye" the RemoteControl is instructing
// the RemoteReceiver to close the connection.
if (str.equalsIgnoreCase("bye")){
socket.close();
break;
}
System.out.println("Processing command " + str);
pw.println(client.message(str));
}
Solution 2
You need to set a read timeout on the socket, with
Socket.setSoTimeout()
. This will cause any read method to throw aSocketTimeoutException
if the read timeout specified expires. NB Read timeouts are set not on the stream but on the underlyingSocket,
viaSocket.setSoTimeout().
There is no such thing as a write timeout in TCP.
Solution 3
You could use SimpleTimeLimiter from Google's Guava library.
Sample code (in Java 8):
BufferedReader br = ...;
TimeLimiter timeLimiter = new SimpleTimeLimiter();
try {
String line = timeLimiter.callWithTimeout(br::readLine, 10, TimeUnit.SECONDS);
} catch (TimeoutException | UncheckedTimeoutException e) {
// timed out
} catch (Exception e) {
// something bad happened while reading the line
}
Solution 4
An answer in this question describes an interesting method using a Timer
to close the connection. I'm not 100% sure if this works in the middle of a read, but it's worth a shot.
Copied from that answer:
TimerTask ft = new TimerTask(){
public void run(){
if (!isFinished){
socket.close();
}
}
};
(new Timer()).schedule(ft, timeout);
isFinished
should be a boolean
variable that should be set to true
when you're done reading from the stream.
codewario
Husband, father, engineer, musician, and retrocomputing-enthusiast
Updated on November 02, 2020Comments
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codewario over 3 years
How does one set a timeout on a BufferedReader and a PrintWriter created using a socket connection? Here is the code I have for the server right now, which works until either the server or the client crashes:
while(isReceiving){ str = null; BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())); PrintWriter pw = new PrintWriter(socket.getOutputStream(), true); while ((str = br.readLine()) != null){ System.out.println("Processing command " + str); pw.println(client.message(str)); } }
Outside the scope of this code I have imposed a socket timeout of 1000ms, which works as intended when waiting for the initial connection. But the program blocks at (str = br.readLine()). If the client hangs or crashes, it never stops blocking unless I terminate the process (which even then doesn't always work).
The client code in question is very similar to this, and is blocking in a similar fashion.
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Vishy almost 13 years+1: I would use socket.close() which closes the socket and streams. You can close it more than once.
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Vishy almost 13 yearsYou could also say what the
isFinished
test is for. ;) -
codewario almost 13 yearsI'll give this a shot, but I'm skepitcal if socket.close() will work because I've already tried closing it that way... no dice. It shouldn't matter if the socket I'm trying to close is in another thread would it?
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codewario almost 13 yearsThis did not work, the br.readLine() still continues to block even after I close the socket. I did found a workaround though, I will post it as an answer shortly.
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codewario almost 13 yearsAbove I posted my workaround for getting the desired behavior in my case, but there is no way to stop the block in this case? As noted in my question, I invoke socket.setSoTimeout(1000L) outside of what I did post, so shouldn't the socket time out at that point and end all read and write operations on the socket?
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user207421 almost 13 years@MetalSearGolid It should end read operations, with a SocketTimeoutException after the read has blocked for the timeout period. As i have already stated, there is no write timeout in TCP.
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user207421 over 8 yearsIf you can send "bye" you can just close the socket, which will cause
readLine()
at the peer to return null. Hard to see how this solves the problem you stated. -
Force almost 8 yearsThe posted link is dead, you can find the project now at github.com/google/guava/tree/master/guava/src/com/google/common/…
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Philipp Jardas almost 8 yearsUpdated my answer. Thanks!
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Alkanshel almost 8 years...Java 8. The question said Java 1.4.
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codewario over 7 yearsIt's been a while since I asked this question, but if memory serves the listening process continued to hang after closing the socket from the client. I remember that we were using some hokey customized implementation of Java which didn't always behave in the way one might expect.
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user207421 over 7 yearsWhat you claim is not possible. Please retest it.
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Philipp Jardas over 7 yearsThe principle described will work perfectly with Java 1.4 -- the only difference is the syntax.
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user207421 about 6 years@BendertheGreatest Not possible. You would have got a
socket closed
exception. -
user207421 about 6 yearsThe Guava code only works if the
read()
method concerned is interruptible.java.net.Socket
reads are not. -
LWChris over 5 years@user207421 There is a method
callUninterruptiblyWithTimeout
. The source has a lot of switches to distinguish between interruptible and uninterruptible methods, so it seems to be aware and ready for other usecases. -
user207421 almost 4 years@YoussefDir That sets a read timeout, as I already stated in the answer. Not a write timeout,
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user207421 almost 4 years@LWChris Did you read it? 'The difference with
callWithTimeout()
is that this method will Ignore interrupts on the current thread'. You can't just magically make an uninterruptible call interruptible, and this library doesn't do so, or claim to. -
LWChris almost 4 years@MarquisofLorne I read it again; I think I had misinterpreted "callUninterruptibly" for "callUninterruptable". The "callWithTimeout" becomes uninterruptable, the callable argument still has to be. Sorry for the confusion.