[ Previous | Next | Table of Contents | Index | Library Home |
Legal |
Search ]
Technical Reference: Communications, Volume 2
Get protocol-specific service
information.
X/Open Transport Interface
Library (libxti.a)
#include <xti.h>
int t_getinfo (fd, info)
int fd;
struct t_info *info;
The t_getinfo
subroutine returns the current characteristics of the underlying transport
protocol and/or transport connection associated with the file descriptor
specified by the fd parameter. The pointer specified by the
info parameter returns the same information returned by the
t_open subroutine, although not necessarily precisely the same
values. This subroutine enables a transport user to access this
information during any phase of communication.
fd
| Specifies the file descriptor.
|
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 functions */
long discon; /* max amount of data allowed on t_snddis */
/* and t_rcvdis functions */
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 options set by
users.
|
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 datastream 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 (see Appendix A, ISO Transport Protocol Information and
Appendix B, Internet Protocol-specific Information)
.
|
connect
| A value greater than zero specifies the maximum amount of data that may
be associated with connection establishment functions and a value of -2
specifies that the transport provider does not allow data to be sent with
connection establishment functions.
|
discon
| A value greater than zero specifies the maximum amount of data that may
be associated with the t_snddis 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 functions.
|
servtype
| This field specifies the service type supported by the transport provider
on return. The possible values 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, the t_open subroutine will return -2 for
etsdu, connect and
discon.
|
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 that the underlying transport provider supports the sending of
zero-length TSDUs. See Appendix A, ISO Transport Protocol Information
for a discussion of the separate issue of zero-length fragments within a
TSDU.
|
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 results if a transport user exceeds the allowed data
size on any subroutine. The value of each field may change as a result
of protocol option negotiation during connection establishment (the
t_optmgmt call has no affect on the values returned by the
t_getinfo subroutine). These values will only change from
the values presented to the t_open subroutine after the endpoint
enters the T_DATAXFER state.
ALL - apart from T_UNINIT.
0
| Successful completion.
|
-1
| 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.
|
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_alloc subroutine, t_open subroutine.
[ Previous | Next | Table of Contents | Index |
Library Home |
Legal |
Search ]