Which ancient poem is written as a communication tool of history?

Hope in Spring, A Word to Secretary Hu Ling and so on. We can see from Du Fu's "Spring Hope" that the ancient way of communication is letters, and from Li Shangyin's "A Letter to Secretary Ling Huchong", we can see that the ancient way of communication is letters. There were many communication tools in ancient times, such as flying pigeons passing books, beating drums and ringing gold, showing smoke and burning fire, scouts exploring horses, signal flares, darts passing books, books drifting along the river and so on. Communication is an important means for people to communicate socially.