The first successful message on the ARPANET was sent by UCLA student programmer Charley Kline, at 10:30 pm PST on 29 October 1969 (6:30 UTC on 30 October 1969), from Boelter Hall 3420.[44] Kline transmitted from the university’s SDS Sigma 7 Host computer to the Stanford Research Institute’s SDS 940 Host computer. The message text was the word login; on an earlier attempt the l and the o letters were transmitted, but the system then crashed. Hence, the literal first message over the ARPANET was lo. About an hour later, after the programmers repaired the code that caused the crash, the SDS Sigma 7 computer effected a full login.[45] The first permanent ARPANET link was established on 21 November 1969, between the IMP at UCLA and the IMP at the Stanford Research Institute. By 5 December 1969, the entire four-node network was established.
https://en.wikipedia.org/wiki/ARPANET
