.\" $Id$ .\" .\" Copyright 1998 by the Massachusetts Institute of Technology. .\" .\" Permission to use, copy, modify, and distribute this .\" software and its documentation for any purpose and without .\" fee is hereby granted, provided that the above copyright .\" notice appear in all copies and that both that copyright .\" notice and this permission notice appear in supporting .\" documentation, and that the name of M.I.T. not be used in .\" advertising or publicity pertaining to distribution of the .\" software without specific, written prior permission. .\" M.I.T. makes no representations about the suitability of .\" this software for any purpose. It is provided "as is" .\" without express or implied warranty. .\" .TH ARES_GETHOSTBYADDR 3 "24 July 1998" .SH NAME ares_gethostbyaddr \- Initiate a host query by address .SH SYNOPSIS .nf .B #include <ares.h> .PP .B typedef void (*ares_host_callback)(void *\fIarg\fP, int \fIstatus\fP, .B int \fItimeouts\fP, struct hostent *\fIhostent\fP) .PP .B void ares_gethostbyaddr(ares_channel \fIchannel\fP, const void *\fIaddr\fP, .B int \fIaddrlen\fP, int \fIfamily\fP, ares_host_callback \fIcallback\fP, .B void *\fIarg\fP) .fi .SH DESCRIPTION The .B ares_gethostbyaddr function initiates a host query by address on the name service channel identified by .IR channel . The parameters .I addr and .I addrlen give the address as a series of bytes, and .I family gives the type of address. When the query is complete or has failed, the ares library will invoke \fIcallback\fP. Completion or failure of the query may happen immediately, or may happen during a later call to \fIares_process(3)\fP, \fIares_destroy(3)\fP or \fIares_cancel(3)\fP. .PP The callback argument .I arg is copied from the .B ares_gethostbyaddr argument .IR arg . The callback argument .I status indicates whether the query succeeded and, if not, how it failed. It may have any of the following values: .TP 19 .B ARES_SUCCESS The host lookup completed successfully. .TP 19 .B ARES_ENOTIMP The ares library does not know how to look up addresses of type .IR family . .TP 19 .B ARES_ENOTFOUND The address .I addr was not found. .TP 19 .B ARES_ENOMEM Memory was exhausted. .TP 19 .B ARES_EDESTRUCTION The name service channel .I channel is being destroyed; the query will not be completed. .PP The callback argument .I timeouts reports how many times a query timed out during the execution of the given request. .PP On successful completion of the query, the callback argument .I hostent points to a .B struct hostent containing the name of the host returned by the query. The callback need not and should not attempt to free the memory pointed to by .IR hostent ; the ares library will free it when the callback returns. If the query did not complete successfully, .I hostent will be .BR NULL . .SH SEE ALSO .BR ares_process (3), .BR ares_gethostbyname (3) .SH AUTHOR Greg Hudson, MIT Information Systems .br Copyright 1998 by the Massachusetts Institute of Technology.