T_CONNECT(3NSL)T_CONNECT(3NSL)NAMEt_connect - establish a connection with another transport user
SYNOPSIS
#include <xti.h>
int t_connect(int fd, const struct t_call *sndcall,
struct t_call *rcvcall);
DESCRIPTION
This routine is part of the XTI interfaces which evolved from the TLI
interfaces. XTI represents the future evolution of these interfaces.
However, TLI interfaces are supported for compatibility. When using a
TLI routine that has the same name as an XTI routine, the tiuser.h
header file must be used. Refer to the TLI COMPATIBILITY section for
a description of differences between the two interfaces. This function
enables a transport user to request a connection to the specified des‐
tination transport user.
This function can only be issued in the T_IDLE state. The parameter fd
identifies the local transport endpoint where communication will be
established, while sndcall and rcvcall point to a t_call structure
which contains the following members:
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
int sequence;
The parameter sndcall specifies information needed by the transport
provider to establish a connection and rcvcall specifies information
that is associated with the newly established connection.
In sndcall, addr specifies the protocol address of the destination
transport user, opt presents any protocol-specific information that
might be needed by the transport provider, udata points to optional
user data that may be passed to the destination transport user during
connection establishment, and sequence has no meaning for this func‐
tion.
On return, in rcvcall, addr contains the protocol address associated
with the responding transport endpoint, opt represents any protocol-
specific information associated with the connection, udata points to
optional user data that may be returned by the destination transport
user during connection establishment, and sequence has no meaning for
this function.
The opt argument permits users to define the options that may be passed
to the transport provider. The user may choose not to negotiate proto‐
col options by setting the len field of opt to zero. In this case, the
provider uses the option values currently set for the communications
endpoint.
If used, sndcall→opt.buf must point to a buffer with the corresponding
options, and sndcall→opt.len must specify its length. The maxlen and
buf fields of the netbuf structure pointed by rcvcall→addr and rcv‐
call→opt must be set before the call.
The udata argument enables the caller to pass user data to the destina‐
tion transport user and receive user data from the destination user
during connection establishment. However, the amount of user data must
not exceed the limits supported by the transport provider as returned
in the connect field of the info argument of t_open(3NSL) or t_get‐
info(3NSL). If the len of udata is zero in sndcall, no data will be
sent to the destination transport user.
On return, the addr, opt and udata fields of rcvcall will be updated to
reflect values associated with the connection. Thus, the maxlen field
of each argument must be set before issuing this function to indicate
the maximum size of the buffer for each. However, maxlen can be set to
zero, in which case no information to this specific argument is given
to the user on the return from t_connect(). If maxlen is greater than
zero and less than the length of the value, t_connect() fails with
t_errno set to TBUFOVFLW. If rcvcall is set to NULL, no information
at all is returned.
By default, t_connect() executes in synchronous mode, and will wait for
the destination user's response before returning control to the local
user. A successful return (that is, return value of zero) indicates
that the requested connection has been established. However, if O_NON‐
BLOCK is set by means of t_open(3NSL) or fcntl(2), t_connect() exe‐
cutes in asynchronous mode. In this case, the call will not wait for
the remote user's response, but will return control immediately to the
local user and return -1 with t_errno set to TNODATA to indicate that
the connection has not yet been established. In this way, the function
simply initiates the connection establishment procedure by sending a
connection request to the destination transport user. The t_rcvcon‐
nect(3NSL) function is used in conjunction with t_connect() to deter‐
mine the status of the requested connection.
When a synchronous t_connect() call is interrupted by the arrival of a
signal, the state of the corresponding transport endpoint is T_OUTCON,
allowing a further call to either t_rcvconnect(3NSL), t_rcvdis(3NSL) or
t_snddis(3NSL). When an asynchronous t_connect() call is interrupted by
the arrival of a signal, the state of the corresponding transport end‐
point is T_IDLE.
RETURN VALUES
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.
VALID STATES
T_IDLE
ERRORS
On failure, t_errno is set to one of the following:
TACCES
The user does not have permission to use the specified
address or options.
TADDRBUSY
This transport provider does not support multiple con‐
nections with the same local and remote addresses. This
error indicates that a connection already exists.
TBADADDR
The specified protocol address was in an incorrect for‐
mat or contained illegal information.
TBADDATA
The amount of user data specified was not within the
bounds allowed by the transport provider.
TBADF
The specified file descriptor does not refer to a trans‐
port endpoint.
TBADOPT
The specified protocol options were in an incorrect for‐
mat or contained illegal information.
TBUFOVFLW
The number of bytes allocated for an incoming argument
(maxlen) is greater than 0 but not sufficient to store
the value of that argument. If executed in synchronous
mode, the provider's state, as seen by the user, changes
to T_DATAXFER, and the information to be returned in
rcvcall is discarded.
TLOOK
An asynchronous event has occurred on this transport
endpoint and requires immediate attention.
TNODATA
O_NONBLOCK was set, so the function successfully initi‐
ated the connection establishment procedure, but did not
wait for a response from the remote user.
TNOTSUPPORT
This function is not supported by the underlying trans‐
port provider.
TOUTSTATE
The communications endpoint referenced by fd is not in
one of the states in which a call to this function is
valid.
TPROTO
This error indicates that a communication problem has
been detected between XTI and the transport provider for
which there is no other suitable XTI error (t_errno).
TSYSERR
A system error has occurred during execution of this
function.
TLI COMPATIBILITY
The XTI and TLI interface definitions have common names but use differ‐
ent header files. This, and other semantic differences between the two
interfaces are described in the subsections below.
Interface Header
The XTI interfaces use the header file, xti.h. TLI interfaces should
not use this header. They should use the header:
#include <tiuser.h>
Error Description Values
The TPROTO and TADDRBUSY t_errno values can be set by the XTI interface
but not by the TLI interface.
A t_errno value that this routine can return under different circum‐
stances than its XTI counterpart is TBUFOVFLW. It can be returned even
when the maxlen field of the corresponding buffer has been set to zero.
Option Buffers
The format of the options in an opt buffer is dictated by the transport
provider. Unlike the XTI interface, the TLI interface does not fix the
buffer format.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT Level │ Safe │
└───────────────┴─────────────────┘
SEE ALSOfcntl(2), t_accept(3NSL), t_alloc(3NSL), t_getinfo(3NSL), t_lis‐
ten(3NSL), t_open(3NSL), t_optmgmt(3NSL), t_rcvconnect(3NSL),
t_rcvdis(3NSL), t_snddis(3NSL), attributes
May 7, 1998 T_CONNECT(3NSL)
