Send data over the transport connection with write(2). tirdwr passes data through to the transport provider. If you send a zero-length data packet, which the mechanism allows, tirdwr discards the message. If the transport connection is aborted--for example, because the remote user aborts the connection using t_snddis(3NSL)--a hang-up condition is generated on the stream, further write(2) calls fail, and errno is set to ENXIO. You can still retrieve any available data after a hang-up.