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Technical Reference: Base Operating System and Extensions , Volume 2

t_sndreldata Subroutine


Initiate/respond to an orderly release with user data.



#include <xti.h>
int t_sndreldata(int fd, struct t_discon *discon)


This function is used to initiate an orderly release of the outgoing direction of data transfer and to send user data with the release. The argument fd identifies the local transport endpoint where the connection exists, and discon points to a t_discon structure containing the following members:

struct netbuf udata;
int reason;
int sequence;

After calling t_sndreldata, the user may not send any more data over the connection. However, a user may continue to receive data if an orderly release indication has not been received.

The field reason specifies the reason for the disconnection through a protocol-dependent reason code, and udata identifies any user data that is sent with the disconnection; the field sequence is not used.

The udata structure specifies the user data to be sent to the remote user. The amount of user data must not exceed the limits supported by the transport provider, as returned in the discon field of the info argument of t_open or t_getinfo. If the len field of udata is zero or if the provider did not return T_ORDRELDATA in the t_open flags, no data will be sent to the remote user.

If a user does not wish to send data and reason code to the remote user, the value of discon may be a null pointer.

This function is an optional service of the transport provider, only supported by providers of service type T_COTS_ORD. The flag T_ORDRELDATA in the info->flag field returned by t_open or t_getinfo indicates that the provider supports orderly release user data; when the flag is not set, this function behaves as t_rcvrel and no user data is returned.

This function may not be available on all systems.

Parameters Before call After call
fd x /
discon-> udata.maxlen /
discon-> udata.len x
discon-> udata.buf ?(?)
discon-> reason ?
discon-> sequence /

Valid States


Error Codes

On failure, t_errno is set to one of the following:

The amount of user data specified was not within the bounds allowed by the transport provider, or user data was supplied and the provider did not return T_ORDRELDATA in the t_open flags.

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

O_NONBLOCK was set, but the flow control mechanism prevented the transport provider from accepting the function at this time.

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

Orderly release is not supported by the underlying transport provider.

The communications endpoint referenced by fd is not in one of the states in which a call to this function is valid.

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).

A system error has occurred during execution of this function.

Return Value

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.

Related Information

The t_getinfo, t_open, t_rcvreldata (t_rcvreldata Subroutine), t_rcvrel, and t_sndrel subroutines.

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