What is the role of "moon" in looking at the moon and thinking of one far away's poem?

In looking at the moon and thinking of one far away's poem, the role of "Moon" in this poem is to take advantage of the scenery to express feelings for distant relatives.

Zhang Jiuling, looking at the moon and thinking of one far away

the moon, grown full now over the sea, Tianya * * * At this time.

brings to separated hearts, the long thoughtfulness of night.

it is no darker though I blow out my candle, it is no warmer though I put on my coat.

so I leave my message with the moon, and turn to my bed, hoping for dreams.

looking at the moon and thinking of one far away is the work of Zhang Jiuling, a poet in the Tang Dynasty. This poem is a masterpiece of longing for the moon. Close to the topic at the beginning, the first sentence is "Looking at the Moon" and the second sentence is "Huaiyuan"; Then express the feelings of missing relatives far away; Five or six sentences follow three or four sentences, specifically describing the situation of sleepless nights; The last two sentences further express the deep affection for distant relatives. The language of the whole poem is naturally muddy without showing traces, with lingering feelings but no sadness, quiet and beautiful artistic conception, ingenious conception, blending scenes, nuanced and touching.