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Technical Reference: Communications, Volume 2
Receive a data unit.
X/Open Transport Interface
Library (libxti.a)
#include <xti.h>
int t_rcvudata (fd, unitdata, flags)
int fd;
struct t_unitdata *unitdata;
int *flags;
The t_rcvudata
subroutine is used in connectionless mode to receive a data unit from another
transport user.
By default, the
t_rcvudata subroutine operates in synchronous mode and waits for a
data unit to arrive if none is currently available. However, if
O_NONBLOCK is set (via the t_open subroutine or
fcntl), the t_rcvudata subroutine executes in
asynchronous mode and fails if no data units are available.
If the buffer defined in the
udata field of the unitdata parameter is not large
enough to hold the current data unit, the buffer is filled and
T_MORE is set in the flags parameter on return to
indicate that another t_rcvudata subroutine should be called to
retrieve the rest of the data unit. Subsequent calls to the
t_rcvudata subroutine return zero for the length and options until
the full data unit is received.
| fd
| Identifies the local transport endpoint through which data will be
received.
|
| unitdata
| Holds information associated with the received data unit. The
unitdata parameter points to a t_unitdata structure
containing the following members:
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
On return from this call:
- addr
- Specifies the protocol address of the sending user.
- opt
- Identifies options that were associated with this data unit.
- udata
- Specifies the user data that was received.
The maxlen field of
addr, opt, and udata must be set before calling this
subroutine to indicate the maximum size of the buffer for each.
|
| flags
| Indicates that the complete data unit was not received.
|
T_IDLE
Upon successful completion, a
value of 0 is returned. Otherwise, a value of -1 is returned and
t_errno is set to indicate an error.
On failure, t_errno is
set to one of the following:
| TBADF
| The specified file descriptor does not refer to a transport
endpoint.
|
| TBODATA
| O_NONBLOCK 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 (maxlen) is greater than 0 but not sufficient to store the
information. The unit data information to be returned in the
unitdata parameter is discarded.
|
| TLOOK
| An asynchronous event has occurred on the transport endpoint and requires
immediate attention.
|
| TNOTSUPPORT
| This subroutine is not supported by the underlying transport
provider.
|
| TOUTSTATE
| The subroutine was issued in the wrong sequence on the transport endpoint
referenced by the fd parameter.
|
| TPROTO
| This error indicates that a communication problem has been detected
between the X/Open Transport Interface and the transport provider for which
there is no other suitable X/Open Transport Interface
(t_errno).
|
| TSYSERR
| A system error has occurred during execution of this subroutine.
|
The fcntl subroutine, t_alloc subroutine, t_open subroutine, t_rcvuderr subroutine, t_sndudata subroutine.
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