In just four short lines, the speaker paints himself as a wandering performer, one of those old-fashioned minstrels who plays music for whatever he can get. His companions are an odd bunch: a seaman, a barber, and a half moon, which he drinks with as if it were another person at the table. That small touch makes the night feel both friendly and a little lonely, as though the moon is the only regular who always shows up.
The money side of the life is plain. He plays the harp "for a bit of meat," so he is paid in food, not coins. The last line, "send broke thoughts," is the most interesting. It suggests he is penniless, and perhaps that his thoughts are sent off to someone far away, though the poem doesn't say who. The mood is quiet, wry and humble. There's no self-pity, just a matter-of-fact picture of a poor but oddly free life, shared with strangers and the night sky.