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dhcp_acquire

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int dhcp_acquire( void );

Description

This function acquires a DHCP lease that has not yet been obtained, or has expired, or was relinquished using dhcp_release(). Normally, DHCP leases are renewed automatically, however if the DHCP server is down for an extended period then it might not be possible to renew the lease in time, in which case the lease expires and TCP/IP should not be used. When the lease expires, tcp_tick() will return 0, and the global variable for the IP address will be reset to 0. At some later time, this function can be called to try to obtain an IP address.

This function blocks until the lease is renewed, or the process times out.

Return value

 0: OK, lease was not expired, or an IP address lease was acquired with the same IP address as previously obtained.

-1: An error occurred, no IP address is available. TCP/IP functionality is thus not available. Usual causes of an error are timeouts because a DHCP or BOOTP server is not available within the timeout specified by the global variable _bootptimeout (default 30 seconds).

 1: Lease was re-acquired, however the IP address differs from the one previously obtained. All existing sockets must be re-opened. Normally, DHCP servers are careful to reassign the same IP address previously used by the client, however this is sometimes not possible.

Library

BOOTP.LIB