t_connect(3xti)

t_connect -- establish a connection with another transport user

Synopsis

cc [options] file -lnsl

#include <xti.h>

int t_connect(int fd, struct t_call sndcall struct t_call rcvcall)

Description

This TLI/XTI routine enables a transport user to request a connection to the specified destination transport user.

This function is a service of connection-mode transport providers and is supported only if the provider returned service type T_COTS or T_COTS_ORD on t_open or t_getinfo.

sndcall specifies information needed by the transport provider to establish a connection and rcvcall specifies information that is associated with the newly established connection.

Parameters

fd: the file descriptor for the transport endpoint where the connection will be established.
sndcall: points to the t_call structure used to identify the transport user sending the connection indication.
rcvcall: points to the t_call structure used to identify the transport user that will receive the connection indication.

Structure definitions

The pointers sndcall and rcvcall refer to a t_call structure that contains the following members:

   struct netbuf addr;     /* address              */
   struct netbuf opt;      /* options              */
   struct netbuf udata;    /* user data            */
   int sequence;           /* sequence number      */

netbuf is described in intro(3xti). 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 function.

On return in rcvcall, addr returns the protocol address associated with the responding transport endpoint, opt presents 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 implies no structure on the options that may be passed to the transport provider. These options are specific to the underlying protocol of the transport provider. The user may choose not to negotiate protocol options by setting the len field of opt to 0. In this case, the provider may use default options.

The udata argument enables the caller to pass user data to the destination 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 or t_getinfo. If the len (see netbuf in intro(3xti)) field of udata is 0 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 (see the description of netbuf in intro(3xti)) field of each argument must be set before issuing this function to indicate the maximum size of the buffer for each. However, rcvcall may be NULL, in which case no information is given to the user on return from t_connect.

State transitions

On entry, T_IDLE; T_OUTCON or TDATAXFER (successful) or T_IDLE (failed) on exit. If t_connect fails with a TLOOK or TNODATA error, a change of state may occur.

Files

/usr/lib/libxti.so: X/Open^® Transport Interface Library (shared object)
/usr/lib/libnsl.so: Network Services Library (shared object)

Usage

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 0) indicates that the requested connection has been established. However, if O_NONBLOCK is set (via t_open or fcntl), t_connect executes in asynchronous mode. In this way, the function simply initiates the connection establishment procedure by sending a connect request to the destination transport user, and may fail with t_error set to TNODATA.

Also, in the case of the TCP protocol, the peer TCP, and not the peer transport user, confirms the connection. One consequence of this fact is that the t_connect can return success, even though the remote server process may (later) call t_snddis, rather than t_accept, thus aborting the connection.

Return values

t_connect returns 0 on success and -1 on failure and t_errno is set to indicate the error.

Errors

On failure, t_errno may be set to one of the following:

TBADF: The specified file descriptor does not refer to a transport endpoint.
TOUTSTATE: The function was issued in the wrong sequence.
TNODATA: O_NONBLOCK was set (by t_open or cntl) so the function executed in asynchronous mode. Therefore, the connection establishment procedure was successfully executed, but the function did not wait for a response from the remote user.
TBADADDR: The specified protocol address was in an incorrect format or contained invalid information.
TBADOPT: The specified protocol options were in an incorrect format or contained invalid information.
TBADDATA: The amount of user data specified was not within the bounds supported by the transport provider as returned in the connect field of the info argument of t_open or t_getinfo.
TACCES: The user does not have permission to use the specified address or options.
TBUFOVFLW: The number of bytes (maxlen) allocated for an incoming argument is greater than zero 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 connect indication information to be returned in rcvcall is discarded.
TLOOK: An asynchronous event has occurred on the transport endpoint specified by fd 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.
TADDRBUSY: The specified connection already exists, and this transport user does not support multiple connections with the same pair of local and remote addresses.
TPROTO: A communication problem has been detected with the transport provider and there is no other value of t_errno to describe the error condition.

References

fcntl(2), intro(3xti), t_accept(3xti), t_getinfo(3xti), t_listen(3xti), t_open(3xti), t_optmgmt(3xti), t_rcvconnect(3xti)