Shakespeare certainly does have several sonnets that concern the theme of friendship. One of the best examples can be seen in Sonnet 29. This sonnet opens with the speaker feeling in a state of despair and even envy. He feels he has been disgraced by fate and disgraced in the eyes of men. He paints himself as being all alone, feeling rejected, abandoned, and outcast by fellow mankind. The speaker even proclaims he feels envious of other men, envious of men who have more hope than he has, more friends, more skills, and a greater outlook. However, the speaker then says he thinks about a nameless person and that thinking of this nameless person and his or her "sweet love" changes the speaker's state of mind so that now he feels hopeful, uplifted, and wouldn't change his situation for all the wealth of kings, as we see in his final five lines:
Happily I think on thee, and then my state,
Like to the lark at break of day arising
From sullen earth, sings hymns at heaven's gate;
For thy sweet love remember'd such wealth brings
That then I scorn to change my state with kings. (Sonnet 29)
Since nearly thinking of this unnamed person and his or her love for the speaker makes the speaker feel happy and ready to accept his situation, we can see that this poem describes a perfect example of love in the form of friendship.
Shakespeare's Sonnet 30 is also a perfect example of a sonnet portraying the theme of friendship. In this sonnet, the speaker begins by reflecting on all of the things past that he has lost, even "precious friends hid in death's dateless night," which poetically refers to friends who have already passed away. However, the speaker ends the sonnet in his final couplet by saying that when he thinks of a special "dear friend," then he forgets about all of his losses because the one gain of this friend cancels out all of his previous losses and thinking of this one friend puts an end to all of his sorrows, as we see in his lines:
But while I think on thee, dear friend,
All losses are restored and sorrows end. (Sonnet 30)
Hence we see that in both of these sonnets, friendship is captured as a true and generous love that puts an end to all grief, which certainly is true friendship indeed.