知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 WhatsApp employs a "shop and ahead" mechanism for exchanging messages amongst two consumers. Every time a consumer sends a message, it can be stored on the WhatsApp server, which attempts to ahead it for the addressee, and repeatedly requests acknowledgement of receipt. 分享媒体、文档、位置或联系人信息 打开个人对话或群... https://apps-whatsapp.com/whatsapp-web