t_connect(3xti)

Name

t_connect − establish a connection with another transport user

Syntax

#include <xti.h>
int t_connect(fd, sndcall, rcvcall)
int fd;
struct t_call *sndcall;
struct t_call *rcvcall;

Arguments

fdIdentifies the local transport endpoint where communications is established.

sndcallSpecifies information needed by the transport provider to establish a connection.

rcvcallSpecifies information that is associated with the newly established connection.

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

struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
int sequence;

Description

This function enables a transport user to request a connection to the specified destination transport user. This function can be issued only in the T_IDLE state.

In sndcall, the argument addr specifies the protocol address of the destination transport user. The opt argument presents any protocol-specific information that might be needed by the transport provider. The udata argument points to optional user data that may be passed to the destination transport user during connection establishment. The sequence argument has no meaning for this function.

On return in rcvcall, addr argument returns the protocol address associated with the responding transport endpoint. The opt argument presents any protocol-specific information associated with the connection. The udata argument points to optional user data that may be returned by the destination transport user during connection establishment. The sequence argument has no meaning for this function.

The opt argument permits users to define the options that can be passed to the transport provider. These options are specific to the underlying protocol of the transport provider. The user can choose not to negotiate protocol options by setting the len field of opt to zero. In this case, the provider may use default options.

Parameters	Before Call	After Call
resfd	x	/
sndcall->addr.maxlen	/	/
sndcall->addr.len	x	/
sndcall->addr.buf	x(x)	/
sndcall->opt.maxlen	/	/
sndcall->opt.len	x	/
sndcall->opt.buf	?(?)	/
sndcall->udata.maxlen	/	/
sndcall->udata.len	x	/
sndcall->udata.buf	?(?)	/
sndcall->sequence	/	/
rcvcall->addr.maxlen	x	/
rcvcall->addr.len	/	x
rcvcall->addr.buf	x	(x)
rcvcall->opt.maxlen	x	/
rcvcall->opt.len	/	x
rcvcall->opt.buf	x	(x)
rcvcall->udata.maxlen	x	/
rcvcall->udata.len	/	x
rcvcall->udata.buf	x	(?)
rcvcall->sequence	/	/

If used, sndcall->opt.buf structure must point to the corresponding options structures (isoco_options, isocl_options or tcp_options). The maxlen and buf fields of the netbuf structure pointed by rcvcalladdr and rcvcall->opt must be set before the call.

The udata argument enables the caller to pass user data to the destination transport 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(). If the len of udata is zero in sndcall, no data are sent to the destination transport user.

On return, the addr, opt, and udata fields of rcvcall updates 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, rcvcall can be NULL, in which case no information is given to the user on return from t_connect().

By default, t_connect() executes in synchronous mode and waits for the destination user’s response before returning control to the local user. A successful return (that is, a return value of zero) indicates that the requested connection has been established. However, if O_NONBLOCK is set by means of t_open() or fcntl(), t_connect() executes in asynchronous mode. In this case, the call waits for the remote user’s response but returns control immediately to the local user and returns −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 connect request to the destination transport user. The t_rcvconnect() function is used in conjunction with t_connect() to determine the status of the requested connection.

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 the error.

Diagnostics

On failure, t_errno is 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, so the function successfully initiated the connection establishment procedure but did not wait for a response from the remote user.

[TACCES] The user does not have permission to use the specified address or options.

[TBADOPT] The specified protocol options were in an incorrect format or contained illegal information.

[TBADADDR] The specified protocol address was in an incorrect format or contained illegal information.

[TBADDATA] The amount of user data specified was not within the bounds allowed by the transport provider.

[TBUFOVFLW] The number of bytes allocated for an incoming argument is 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 this transport endpoint 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.

Museum

Related Articles