Leonard Kleinrock never imagined Facebook, Twitter, or YouTube that day 40 years ago when his team gave birth to what is now taken for granted as the internet.

"We are constantly surprised by the applications that come along," Kleinrock told AFP as he and others at the University of California, Los Angeles (UCLA) prepared to throw the internet a 40th birthday party on Thursday.

"It's a teenager now. It's learned some things but it has a long way to go. It's behaving erratically, but it's given enormous gratification to its parents and the community."

On 29 October 1969 Kleinrock led a team that got a computer at UCLA to "talk" to one at a research institute.

Kleinrock was driven by a certainty that computers were destined to speak to each other and that the resulting network should be as simple to use as telephones.

"I thought it would be computer to computer, not people to people," Kleinrock said in a nod to online social networking and content sharing that are hallmarks of the Internet Age.

"I never expected that my 99-year-old mother would be on the internet like she was until she passed away."

A key to getting computers to exchange data was breaking digitised information into packets fired between computers on-demand with no wasting of time, according to Kleinrock.

The first internet message: "Lo"

He had outlined his vision in a 1962 graduate school dissertation published as a book.

"Nobody cared, in particular AT&T," Kleinrock said. "I went to them and they said it wouldn't work and that even if it worked they didn't want anything to do with it."

US telecom colossus AT&T ran lines connecting the computers for ARPANET, a project backed with money from a research arm of the US military.

Engineers began typing "LOG" to log into the distant computer, which crashed after getting the "O."

"So, the first message was 'Lo' as in 'Lo and behold'," Kleinrock recounted. "We couldn't have a better, more succinct first message."

Kleinrock's team logged in on the second try, sending digital data packets between computers on the ARPANET. Computers at two other US universities were added to the network by the end of that year.

"We had four-node network and tested the heck out of it," Kleinrock said. "We were able to break the network at will. It was very valuable to shake those things out early on."

Funding came from the US Advanced Research Projects Agency (ARPA) established in 1958 in response to the launch of a Sputnik space flight by what was then the Soviet Union.

US leaders were in a technology race with Cold War rival Russia.

AFP

In video: Funny ads Most ads tend to be dull and boring, but here are some that will crack you up!

Review: Borderlands With millions of weapons and a cartoony style, 'Borderlands' is a breath of fresh air.

Halo 3: ODST This standalone, almost-full-length expansion to 'Halo 3' is actually remarkably good.