Parameter values set by the application

S
A value or the address of a halfword binary number specifying the descriptor of the socket from which the data is to be written.
IOV
An array of tripleword structures with the number of structures equal to the value in IOVCNT and the format of the structures as follows:
Fullword 1
The address of a data buffer.
Fullword 2
Reserved.
Fullword 3
The length of the data buffer referenced in Fullword 1.
IOVCNT
A fullword binary field specifying the number of data buffers provided for this call.