Sex between two men is implied, but not outright stated
From the book (Basil to Dorian):
"There was that wretched boy in the Guards who committed suicide. You were his great friend. There was Sir Henry Ashton, who had to leave England, with a tarnished name. You and he were inseparable."
However, yes, it is clear that Basil is in love (or at least heavily infatuated) with Dorian, and the subtext was blatant enough that, as per this article,
At the Wilde trials of 1895, the opposing attorneys read aloud from “Dorian Gray,” calling it a “sodomitical book.” Wilde went to prison not because he loved young men but because he flaunted that love, and “Dorian Gray” became the chief exhibit of his shamelessness.