Name
t_rcvudata - receive a data unit
Syntax
#include <tiuser.h>
int t_rcvudata(fd, unitdata, flags)
int fd;
struct t_unitdata *unitdata;
int *flags;
Description
This function is used in connectionless mode to receive a
data unit from another transport user. fd identifies the
local transport endpoint through which data will be
received, unitdata holds information associated with the
received data unit, and flags is set on return to indicate
that the complete data unit was not received. unitdata
points to a t_unitdata structure containing the following
members:
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
The maxlen [see netbuf in intro(NSL)] field of addr, opt,
and udata must be set before issuing this function to
indicate the maximum size of the buffer for each.
On return from this call, addr specifies the protocol
address of the sending user, opt identifies protocol-
specific options that were associated with this data unit,
and udata specifies the user data that was received.
By default, t_rcvudata operates in synchronous mode and will
wait for a data unit to arrive if none is currently
available. However, if O_NDELAY is set (via t_open or
fcntl), t_rcvudata will execute in asynchronous mode and
will fail if no data units are available.
If the buffer defined in the udata field of unitdata is not
large enough to hold the current data unit, the buffer will
be filled and T_MORE will be set in flags on return to
indicate that another t_rcvudata should be issued to
retrieve the rest of the data unit. Subsequent t_rcvudata
call(s) will return zero for the length of the address and
options until the full data unit has been received.
On failure, t_errno may be set to one of the following:
[TBADF] The specified file descriptor does not
refer to a transport endpoint.
[TNODATA] O_NDELAY was set, but no data units are
currently available from the transport
provider.
[TBUFOVFLW] The number of bytes allocated for the
incoming protocol address or options is
not sufficient to store the information.
The unit data information to be returned
in unitdata will be discarded.
[TLOOK] An asynchronous event has occurred on
this transport endpoint and requires
immediate attention.
[TNOTSUPPORT] This function is not supported by the
underlying transport provider.
[TSYSERR] A system error has occurred during
execution of this function.
See Also
intro(NSL), t_rcvuderr(NSL), t_sndudata(NSL).
Network Programmer's Guide.
Diagnostics
The t_rcvudata function returns 0 on successful completion
and -1 on failure, and t_errno is set to indicate the error.
Standards Conformance
t_rcvudata is conformant with:
AT&T SVID Issue 2, Select Code 307-127.
(printed 6/18/89)