recvtimeout

Recvtimeout refers to a setting that controls the maximum time a program will wait for data to be received on a network connection or socket. It is commonly implemented as a receive timeout, and the exact name recvtimeout may appear in various APIs as a parameter or option.

In practice, a receive timeout restricts blocking receive operations. When data is not available within the specified interval, the system returns with an error rather than waiting indefinitely. The precise behavior depends on the platform and socket type. On POSIX systems using the SO_RCVTIMEO option, the timeout is supplied as a struct timeval (seconds and microseconds). If the timeout expires, a blocking socket typically yields -1 from recv with errno set to EAGAIN or EWOULDBLOCK. On Windows, a similar option (SO_RCVTIMEO) uses a DWORD representing milliseconds; a timeout results in a WSAETIMEDOUT error for the corresponding receive call.

Syntax and semantics vary by language and library. In POSIX, the option is set with setsockopt, and the timeout affects subsequent recv calls on the socket. In non-blocking mode, the behavior may differ, as calls can fail immediately with EWOULDBLOCK or EAGAIN without relying on the timeout mechanism.

Practical considerations include ensuring partial data handling is correct (a timeout may occur after some bytes have been read), combining timeouts with multiplexing primitives (select, poll, or epoll) for robust I/O, and choosing appropriate values to balance responsiveness with throughput.

Related concepts include send timeouts and overall connection timeouts, which govern how long a program waits for sends or for establishing connections.