在日常生活中，我们经常使用短信进行沟通，但你是否想过，短信是如何从我们的手机发送到接收者的手机的呢？这其中就涉及到一个关键的概念——短信中心号码PDU。今天，我们就来揭开这个神秘的面纱，了解PDU是如何影响我们的通信体验的。
PDU是什么？
PDU是“Protocol Data Unit”的缩写，意为“协议数据单元”。在短信通信中，PDU指的是短信的数据包格式。它将我们的文字信息转换成手机网络能够识别和传输的格式。
PDU的工作原理
当我们发送一条短信时，手机会将文字信息转换为PDU格式，然后通过移动网络发送到短信中心。短信中心再将这些PDU信息转发给接收者的手机，接收者的手机再将PDU信息转换回文字信息，从而完成短信的发送和接收。
PDU格式
PDU格式包括以下几个部分：
- 协议标识符（PID）：用于标识PDU的类型，例如短信、彩信等。
- 用户数据长度（UDL）：表示用户数据的长度。
- 用户数据（UD）：包含短信的实际内容，如文字、图片、铃声等。
- 可变参数：包括短信中心号码、发送时间等信息。
PDU示例
以下是一个简单的PDU示例：
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