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<h1><a name="kanchor67"></a>Client-Server Timeouts</h1>Every client/server application has to face a problem of
network communications. Luckily modern protocols screen the end-application
from all fixable problems. However there are still physical reasons that can't
be fixed by a protocol: disconnections, power failures, crash of a system on
the other end of communication channel etc. In these cases it is still the
responsibility of the client-server application to exit the connection
gracefully, releasing all resources and protecting data.
<p>In order to achieve an efficient client/server communication
and handling of connection problems the following requirements were defined for
db4o:</p><ul><li value="1">The connection should not
be terminated when both client and server are still alive, even if either
of the machines is running under heavy load. </li><li value="2">Whenever a client dies,
peacefully or with a crash, the server should clean up all resources that
were reserved for the client. </li><li value="3">Whenever a server goes
offline, it should be possible for the client to detect that there is a problem.
</li><li value="4">Since many clients may be
connected at the same time, it makes sense to be careful with the
resources the server reserves for each client. </li><li value="5">A client can be a very
small machine, so it would be good if the client application can work with
a single thread.</li></ul><p>Unfortunately all the requirements are difficult to achieve
for a cross-platform application, as Java and .NET sockets behave differently.</p><p>The current approach tries to keep things as simple as
possible: any connection is closed immediately upon a timeout. In order to
prevent closing connections when there is no communication between client and
server due to reasons different from connection problems a separate timer
thread was created to send messages to the server at a regular basis. The
server must reply to the thread immediately, if this does not happen the
communication channel gets closed. </p><p>This approach works effectively for both client and server side. However
there's are small downside to this. When a server operation takes longer than the timeout, the connection will be closed. You can configure the timeouts for the <a href="../configuration/client/timeout_client_socket.htm">client</a> and the <a href="../configuration/server_configuration.htm">server</a>.</p><p>An easy rule of thumb: </p><ul><li value="1">If you experience clients disconnecting, raise the timeout value.</li><li value="2">If you have a system where clients crash frequently or where the network is
very instable, lower the values, so resources for disconnected clients are
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