"Ever the best of friends, eh, Pip?" This is Joe's way of letting Pip know that he is there to encourage, succor, or just love him.
When Pip becomes apprenticed to Joe at Miss Havisham's house, Joe tells Pip,
"And now, old chap,...may you and me do our duty, both on us by one and another."
While he is apprenticed to Joe, Pip acknowledges the industry and dependability of Joe,
It is not possible to know how far the influence of any amiable, honest-hearted, duty-doing man flies out into the world, but I know right well that any good that intermixed itself with my apprenticeship came of plain, contented Joe, and not of restless, aspiring, discontented me.
After Joe comes to tend to Pip in his sickness after being burned when he saves Miss Havisham, Joe tells Pip,
"Which dear old Pip, old chap....you and me was ever friends. And when you're well enough to go out for a ride--what larks!"