Brendan Russell Sinclair, 43, sent the young boy dozens of sexually explicit text messages, porn videos and nude images in 2007.

Sinclair, who the court heard is HIV positive, also booked train tickets from Canberra to Sydney so the boy could meet him, and concocted cover stories to explain the boy's presence in his Millers Point apartment.

The ACT Supreme Court heard he was caught after the boy's mother went to police and an undercover officer took over corresponding with Sinclair.

Sinclair acknowledged that his actions might be viewed as predatory but said he never intended to meet with the boy.

He told the court his heart bled for the victim because the boy was suicidal and suffering from domestic violence.

Sinclair said he had been the victim of sexual assault himself as a child, had previously worked as a "rent boy", and at the time of the offence was taking drugs and alcohol.

He also said his boyfriend at the time was also corresponding with the victim and could have been responsible for some of the explicit messages sent from Sinclair's phone.

But he told the court he would never commit further offences and did not even wish to speak to anyone under the age of 20.

The court heard Sinclair had had a tragic beginning to life and had a chaotic and dysfunctional lifestyle.

But the Commonwealth argued Sinclair had engaged in substantially manipulative conduct and had bombarded the young boy with explicit material, requests for nude photos and requests for the child to perform sex acts.

He had also tried to cover his tracks, creating a fictitious camping trip that would explain the child's absence from his Canberra home and telling the boy that when he came to Sydney for sex, they would tell neighbours that the boy was a cousin of Sinclair's boyfriend.

Chief Justice Terence Higgins will hand down his sentence at a date to be fixed.