You can also pipe it through zstd on the fly, for data that compresses well you'll often see 1.5 to 3× the raw throughput, so a gigabit link can effectively move 165–330MB/s.

Receiver: socat -u TCP6-LISTEN:1234,reuseaddr STDOUT | zstd -d -c | tar -xpf - -C /destination

Sender: tar -C /source -cf - directory | zstd -T0 -6 -c | socat -u STDIN 'TCP6:[fd42:dead:beef::2]:1234'

-T0 uses all cores. Bump the level above -6 for more compression, drop it for more speed, but if your CPU can't keep up, high levels will actually slow it down. Already compressed data won't see much benefit.