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How can I set Socket write timout in java?
(1 answer)
Closed 5 years ago.
In java, Socket has a method setSoTimeout that can be used to specify the reading timeout, but there is no method to specify the writing timeout
When I　searched google, a lot of responses like "use nio and selectors", it looks that SocketChannel provides the way to specify the writing timeout, I brief the code of this class, but I still didn't find out how to do it.
Could someone show some code or some guide? Thanks
One possible way to mitigate the lack of a timeout option on a write call is to simply just set the SO_SNDBUF size via Socket.setSendBuffer to something very high. This will allow subsequent calls for writing to avoid blocking unless the pipe to the remote side gets backed up. If possible, structure your protocol such that you wait for some sort of response to data already sent before sending more data. That way, you won't ever exceed the send buffer.
YMMV.
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TCP keep-alive to determine if client disconnected in netty
(4 answers)
Closed 6 years ago.
I'm using Java and Netty to connect to a Unity-Client through a TCP/IP connection.
Sometimes the connection can break and the Unity-guy proposed to send a ping (just a one byte message) every 5 seconds and if the time of reception of the last ping is higher than 30 seconds, the connection is lost.
Do I really need to mesure the time? Isn't it enough to trigger an exception if I try to send something through the socket? Is there a case where a write won't detect a connection loss?
I tagged it Netty since I am using it, but it probably is the same with a simple Socket connection.
I think the real answer is: you have to define for yourself how you want your application to behave.
What I mean is: there are many different problems that could occur to your connection. Writing data, and failing immediately when that doesn't work is just one option to handle that.
You can also envision continuous pinging; for example to detect when the other is just "temporarily" unavailable. In other words: you establish some sort of "heartbeat" monitoring; and thus you enable your application for a "wider range" of potential "reactions".
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What is the difference between connection and read timeout for sockets?
(2 answers)
Closed 8 years ago.
Just curiosity. Is there a good reason why the class URLConnection needs to have two different timeouts?
The connectTimeout is the maximum time in milliseconds to wait while connecting. Connecting to a server will fail with a SocketTimeoutException if the timeout elapses before a connection is established.
The readTimeout is the maximum time to wait for an input stream read to complete before giving up. Reading will fail with a SocketTimeoutException if the timeout elapses before data becomes available.
Can you give me a good reason why these two values should be different? Why a call would need more time for performing the connection rather than receiving some data (or viceversa)?
I am asking this because I have to configure these values and my idea is to set the same value for both.
Let's say server is busy and is configured to accept 'N' connection and all the connections are long runner and all of sudden you send in request, What should happen? Should you wait indefinitely or should you time out? That's connectTimeout.
While let's say your server turns brain dead service just accepting connection and doing nothing with it (or say server synchronously goes to db and does some time taking activity and server ends up with deadlock for e.g.) and on the other hand client keeps on waiting for the response, in this case what should client do? Should it wait indefinitely for response or should it timeout? That's read timeout.
The connection timeout is how long you're prepared to wait to get some sort of response from the server. It's not particularly related to what it is that you're trying to achieve.
But suppose you had a service that would allow you to give it a large number, and have it return its prime factors. The server might take quite a while to generate the answer and send it to you.
You might well have clear expectations that the server would quickly respond to the connection: maybe even a delay of 5 seconds here tells you that the server is likely to be down. But the read timeout might need to be much higher: it might be a few minutes before you get to be able to read the server's answer to your query.
The connect time-out is the time-out in which you want a (in normal situations TCP) connection to be established. The default time-outs as specified in the internet RFCs and implemented by the various OSes are normally in the minute(s) range. But we know that if a server is available and reachable, it will respond in a matter of milli-seconds and otherwise not at all. A normal value would be a couple of seconds at a maximum.
The read timeout is the time in which the server is expected to respond after it received the incoming request. Read time-outs therefore depend on time within you expect the server to deliver the result. These are depending on the type of the request you are making and should be larger if the processing requires some time or the server may be very busy in some situations. Especially if you do a retry after a read time-out, it is best to put the read time-outs not too low, normally a factor 3-4 times the expected time.
I am trying to implement a HTTP server using netty & i wanted to know few thing which i could not understand from the netty api. I read many other netty related stackoverflow question but still i couldn't udnertand.
1.If i want the connection from client to be opened for a certain period of time, what should i use CONNECT_TIMEOUT_MILLIS or add a read timeout handler & add a timeout in it. Basically i want to understand the difference between these two. & what is the default value of CONNECT_TIMEOUT_MILLIS.
what is the default value of SO_BACKLOG,i read it in one of the that it is equal to SOMAXCONN in io.netty.netUtils.But what it the value of it. Also, i want to be sure that so_backlog limits the number of worker thread ri8?. I mean if i set it to say 1000 it means netty won't allow more than 1000 open connection at a time.
can somebody explain how netty responds to a HTTP request as in internally in terms of writing & reading from a channel?
Thanks in advance!!!
CONNECT_TIMEOUT_MILLIS is the timeout for connection attempt. Once the connection is established, it has no effect. What you are interested in is ReadTimeoutHandler.
The default SO_BACKLOG is NetUtils.SOMAXCONN. It does not limit the number of worker threads. For more information about SO_BACKLOG, please refer to this question. To limit the number of worker threads, you must specify it when you construct an NioEventLoop. SO_BACKLOG is unrelated to the maximum number of concurrent connections, either.
Re: How HTTP works in Netty - The question is too broad to give a simple answer. Please use your debugger to step into the Netty internals to find our how it works.
One way of limiting the number of concurrent connections is by limiting the number of open files a process can have. This property can be set in Linux using ulimit command or using limits.conf file
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How to detect a remote side socket close? [duplicate]
(4 answers)
Closed 9 years ago.
I've read several questions about this on stack overflow already, but none of them has provided me with an elegant solution.
I know that calling isConnected() and isClosed() on the Socket is useless because it returns the local connection state (if the server is connected - not if the client is connected, as I want).
I also can't simply call if(socket.getInputStream().read()==-1)* because that would only account for the end of the stream (EOS) being reached - i.e., the client didn't send a message recently. This doesn't at all indicate that the client has disconnected however.
I'm considering just having the client send a message to the server letting it know it's disconnecting just before it closes the socket, but I'm wondering if there's a simpler solution I'm missing - wanting to know the connection state of the remote socket is a fairly commonplace desire. Thanks.
*not to mention the fact that InputStream#read() is an abstract method, I'm using DataInputStream for data read methods (i.e. readInt(), readByte(), etc.)
I'm considering just having the client send a message to the server letting it know it's closing just before it closes the socket,
Why? It's pointless. You will read this message instead of getting -1 from read(). The latter is all you need. The extra read() in your post is certainly a bad idea, but the read that reads messages isn't. You need that, and you will get EOS from it. You don't need an extra message to tell you the same thing.
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Timeout for SocketChannel doesn't work
(3 answers)
Closed 4 years ago.
What is the best way to set a timeout to close a NIO SocketChannel if there is no data is received for a certain period after the connection is established?
Either:
You are using a Selector, in which case you have a select timeout which you can play with, and if it goes off (select(timeout) returns zero) you close all the registered channels, or
You are using blocking mode, in which case you might think you should be able to call Socket.setSoTimeout() on the underlying socket (SocketChannel.socket()), and trap the SocketTimeoutException that is thrown when the timeout expires during read(), but you can't, because it isn't supported for sockets originating as channels, or
You are using non-blocking mode without a Selector, in which case you need to change to case (1).
So you either need to use case (1) or a java.net.Socket directly.
I was looking for the same recommendation and could not find it easily - sharing it here.
There is a nice handler for netty called: ReadTimeoutHandler.
One can use it like that
channel.pipeline().addLast(new ReadTimeoutHandler(readTimeout));
it will drop io.netty.handler.timeout.ReadTimeoutException when failed to see any data doing the defined read timeout.