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Technical Reference: Communications, Volume 2
Establish a transport
endpoint.
X/Open Transport Interface
Library (libxti.a)
#include <xti.h>
#include <fcntl.h>
int t_open (
const char *name;
int oflag;
struct t_info *info)
The t_open subroutine
must be called as the first step in the initialization of a transport
endpoint. This subroutine establishes a transport endpoint by supplying
a transport provider identifier that indicates a particular transport provider
(for example, transport protocol) and returning a file descriptor that
identifies that endpoint.
This subroutine also returns
various default characteristics of the underlying transport protocol by
setting fields in the t_info structure.
name
| Points to a transport provider identifier.
|
oflag
| Identifies any open flags (as in the open exec)
. The oflag parameter is constructed from O_RDWR
optionally bitwise inclusive-OR-ed with O_NONBLOCK. These
flags are defined by the fcntl.h header file. The
file descriptor returned by the t_open subroutine is used by all
subsequent subroutines to identify the particular local transport
endpoint.
|
info
| Points to a t_info structure which contains the following
members:
long addr; /* max size of the transport protocol */
/* address */
long options; /* max number of bytes of */
/* protocol-specific options */
long tsdu; /* max size of a transport service data */
/* unit (TSDU) */
long etsdu; /* max size of an expedited transport */
/* service data unit (ETSDU) */
long connect; /* max amount of data allowed on */
/* connection establishment subroutines */
long discon; /* max amount of data allowed on */
/* t_snddis and t_rcvdis subroutines */
long servtype; /* service type supported by the */
/* transport provider */
long flags; /* other info about the transport provider */
The values of the fields have the
following meanings:
- addr
- A value greater than zero indicates the maximum size of a transport
protocol address and a value of -2 specifies that the transport provider does
not provide user access to transport protocol addresses.
- options
- A value greater than zero indicates the maximum number of bytes of
protocol-specific options supported by the provider, and a value of -2
specifies that the transport provider does not support user-settable
options.
- tsdu
- A value greater than zero specifies the maximum size of a transport
service data unit (TSDU); a value of zero specifies that the transport
provider does not support the concept of TSDU, although it does support the
sending of a data stream with no logical boundaries preserved across a
connection; a value of -1 specifies that there is no limit on the size of
a TSDU; and a value of -2 specifies that the transfer of normal data is
not supported by the transport provider.
- etsdu
- A value greater than zero specifies the maximum size of an expedited
transport service data unit (ETSDU); a value of zero specifies that the
transport provider does not support the concept of ETSDU, although it does
support the sending of an expedited data stream with no logical boundaries
preserved across a connection; a value of -1 specifies that there is no
limit on the size of an ETSDU; and a value of -2 specifies that the
transfer of expedited data is not supported by the transport provider.
Note that the semantics of expedited data may be quite different for different
transport providers.
- connect
- A value greater than zero specifies the maximum amount of data that may be
associated with connection establishment subroutines and a value of -2
specifies that the transport provider does not allow data to be sent with
connection establishment subroutines.
- discon
- A value greater than zero specifies the maximum amount of data that may be
associated with the t_synddis and t_rcvdis subroutines
and a value of -2 specifies that the transport provider does not allow data to
be sent with the abortive release subroutines.
|
|
- servtype
- This field specifies the service type supported by the transport
provider. The valid values on return are:
- T_COTS
- The transport provider supports a connection-mode service but does not
support the optional orderly release facility.
- T_COTS_ORD
- The transport provider supports a connection-mode service with the
optional orderly release facility.
- T_CLTS
- The transport provider supports a connectionless-mode service. For
this service type, t_open will return -2 for
etsdu, connect and
discon.
A single transport endpoint may
support only one of the above services at one time.
- flags
- This is a bit field used to specify other information about the transport
provider. If the T_SENDZERO bit is set in flags, this
indicates the underlying transport provider supports the sending of
zero-length TSDUs.
If a transport user is concerned
with protocol independence, the above sizes may be accessed to determine how
large the buffers must be to hold each piece of information.
Alternatively, the t_alloc subroutine may be used to allocate these
buffers. An error will result if a transport user exceeds the allowed
data size on any subroutine.
If the info parameter
is set to a null pointer by the transport user, no protocol information is
returned by the t_open subroutine.
|
T_UNINIT
Valid file descriptor
| Successful completion.
|
-1
| t_errno is set to indicate an error.
|
On failure, t_errno is
set to one of the following:
TBADFLAG
| An invalid flag is specified.
|
TBADNAME
| Invalid transport provider name.
|
TSYSERR
| A system error has occurred during execution of this subroutine.
|
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).
|
The t_open subroutine.
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