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HP-UX 11i Version 3: February 2007

Technical documentation

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t_connect() — establish a connection with another transport user


#include <xti.h> /* for X/OPEN Transport Interface - XTI */ /* or */ #include <tiuser.h> /* for Transport Layer Interface - TLI */ int t_connect (fd, sndcall, rcvcall); int fd; struct t_call *sndcall; struct t_call *rcvcall;


This function enables a transport user to request a connection to the specified destination transport user. This function can only be issued in the T_IDLE state. fd identifies the local transport endpoint where communication will be established. 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 type netbuf structure is defined in the <xti.h> or <tiuser.h> header file. This structure, which is used to define buffer parameters, has the following members:

unsigned int maxlen

maximum byte length of the data buffer

unsigned int len

actual byte length of data written to buffer

char *buf

points to buffer location

sndcall specifies information needed by the transport provider to establish a connection. 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. 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. sequence has no meaning for this function.

The opt argument permits users to define the options that may be passed to the transport provider. These options are specific to the underlying protocols of the transport provider and are described for ISO and TCP protocols in Appendix A, "ISO Transport Protocol Information," Appendix B, "Internet Protocol-specific Information," and Appendix F, "Headers and Definitions" of the CAE Specification X/Open Transport Interface (XTI) manual. The user may choose not to negotiate protocol options by setting the len field of opt to zero. In this case, the provider may use default options.

If the opt argument is used, the sndcall->opt.buf structure must point to the corresponding options structures. For XTI over the OSI transport provider, the options buffer should be a struct of type isoco_options or tcp_options. For TLI, see the documentation for the transport provider being used. The maxlen and buf fields of the netbuf structure pointed by rcvcall->addr and rcvcall->opt must be set before the call.

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 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, rcvcall may be a null pointer, in which case no information is given to the user on return from t_connect().

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 (i.e., return value of zero) 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 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 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.

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(), t_rcvdis(), or t_snddis().

Valid States


Fork Safety

t_connect is not fork-safe.


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.



The specified file descriptor does not refer to a transport endpoint.


The function was issued in the wrong sequence.


O_NONBLOCK was set, so the function successfully initiated the connection establishment procedure, but did not wait for a response from the remote user.


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


The specified protocol options were in incorrect format or contained illegal information.


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


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


The number of bytes allocated for an incoming argument (maxlen) 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.


An asynchronous event has occurred on this transport endpoint and requires immediate attention.


This function is not supported by the underlying transport provider.


A system error has occurred during execution of this function.


This transport provider does not support multiple connections with the same local and remote addresses. This error indicates that a connection already exists.


(XTI only) This error indicates that a communication problem has been detected between XTI and the transport provider for which there is no suitable XTI (t_errno).



XTI data structures


TLI data structures


t_connect(): SVID2, XPG3, XPG4

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