DESCRIPTION
This function is used in connectionless mode to send a data unit to another transport user. The argument
fd identifies the local transport endpoint through which data will be sent,
iovcount contains the number of non-contiguous
udata buffers and is limited to an implementation-defined value given by
T_IOV_MAX which is at least 16, and
unitdata points to a
t_unitdata structure containing the following members:
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
If the limit on
iovcount is exceeded, the function fails with
TBADDATA.
In
unitdata,
addr specifies the protocol address of the destination user, and
opt identifies options that the user wants associated with this request. The
udata field is not used. The user may choose not to specify what protocol options are associated with the transfer by setting the
len field of
opt to zero. In this case, the provider may use default options.
The data to be sent is identified by
iov[0] through
iov [iovcount-1].
Note that the limit on the total number of bytes available in all buffers passed:
iov(0).iov_len + . . + iov(iovcount-1).iov_len
may be constrained by implementation limits. If no other constraint applies, it will be limited by
INT_MAX. In practice, the availability of memory to an application is likely to impose a lower limit on the amount of data that can be sent or received using scatter/gather functions.
By default,
t_sndvudata() operates in synchronous mode and may wait if flow control restrictions prevent the data from being accepted by the local transport provider at the time the call is made. However, if
O_NONBLOCK is set by means of
t_open(3NSL) or
fcntl(2),
t_sndvudata() executes in asynchronous mode and will fail under such conditions. The process can arrange to be notified of the clearance of a flow control restriction by means of either
t_look(3NSL) or the EM interface.
If the amount of data specified in
iov0 through
iov [iovcount-1] exceeds the TSDU size as returned in the
tsdu field of the
info argument of
t_open(3NSL) or
t_getinfo(3NSL), or is zero and sending of zero octets is not supported by the underlying transport service, a
TBADDATA error is generated. If
t_sndvudata() is called before the destination user has activated its transport endpoint (see
t_bind(3NSL)), the data unit may be discarded.
If it is not possible for the transport provider to immediately detect the conditions that cause the errors
TBADADDR and
TBADOPT, these errors will alternatively be returned by
t_rcvuderr(3NSL). An application must therefore be prepared to receive these errors in both of these ways.
ERRORS
On failure,
t_errno is set to one of the following:
TBADADDR
The specified protocol address was in an incorrect format or contained illegal information.
TBADDATA
Illegal amount of data.
-
o
-
A single send was attempted specifying a TSDU greater than that specified in the info argument, or a send of a zero byte TSDU is not supported by the provider.
-
o
-
iovcount is greater than T_IOV_MAX.
TBADF
The specified file descriptor does not refer to a transport endpoint.
TBADOPT
The specified options were in an incorrect format or contained illegal information.
TFLOW
O_NONBLOCK i was set, but the flow control mechanism prevented the transport provider from accepting any data at this time.
TLOOK
An asynchronous event has occurred on this transport endpoint.
TNOTSUPPORT
This function is not supported by the underlying transport 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.