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connection timeout — a time period in which a client should establish a connection with a server. socket timeout — a maximum time of inactivity between two data packets when exchanging data with a server.
Read Timed Out From the server side, it happens when the server takes a long time to read data compared to the preset timeout.
If the TCP handshake is not completed in this time, the connection attempt failed. The read timeout is the time-out applied from the moment you have established a connection (So handshaking is done, and the connection can be used). If no data comes from the server in this time-out time, the connection is terminated.
Connection timeout is a common error that occurs whenever the client is waiting for too long before getting a response from any server (for API calls or browser requesting pages).
- What is the difference between connection and read timeout for sockets?
The connection timeout is the timeout in making the initial connection; i.e. completing the TCP connection handshake. The read timeout is the timeout on waiting to read data1. If the server (or network) fails to deliver any data <timeout> seconds after the client makes a socket read call, a read timeout error will be raised.
- What does connection timeout set to "infinity" mean? In what situation can it remain in an infinitive loop? and what can trigger that the infinity-loop dies?
It means that the connection attempt can potentially block for ever. There is no infinite loop, but the attempt to connect can be unblocked by another thread closing the socket. (A Thread.interrupt() call may also do the trick ... not sure.)
- What does read timeout set to "infinity" mean? In what situation can it remain in an infinite loop? What can trigger that the infinite loop to end?
It means that a call to read on the socket stream may block for ever. Once again there is no infinite loop, but the read can be unblocked by a Thread.interrupt() call, closing the socket, and (of course) the other end sending data or closing the connection.
1 - It is not ... as one commenter thought ... the timeout on how long a socket can be open, or idle.
These are timeout values enforced by JVM for TCP connection establishment and waiting on reading data from socket.
If the value is set to infinity, you will not wait forever. It simply means JVM doesn't have timeout and OS will be responsible for all the timeouts. However, the timeouts on OS may be really long. On some slow network, I've seen timeouts as long as 6 minutes.
Even if you set the timeout value for socket, it may not work if the timeout happens in the native code. We can reproduce the problem on Linux by connecting to a host blocked by firewall or unplugging the cable on switch.
The only safe approach to handle TCP timeout is to run the connection code in a different thread and interrupt the thread when it takes too long.
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