eCosPro® Reference Manual
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# Application polling

When a connection is idle (i.e., no data is either transmitted or received), lwIP will repeatedly poll the application by calling a specified callback function. This can be used either as a watchdog timer for killing connections that have stayed idle for too long, or as a method of waiting for memory to become available. For instance, if a call to `tcp_write()` has failed because memory wasn't available, the application may use the polling functionality to call `tcp_write()` again when the connection has been idle for a while.

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tcp_recved() | Up | tcp_poll()