目前较为常用的串口有9针串口（DB9）和25针串口（DB25），通信距离较近时(<12m)，可以用电缆线直接连接标准RS232端口(RS422,RS485较远)，若距离较远，需附加调制解调器（MODEM）。最为简单且常用的是三线制接法，即地、接收数据和发送数据三脚相连，本文只涉及到最为基本的接法，且直接用RS232相连，以回答前段网友的咨询-There are currently more commonly used 9-pin serial port (DB9) and 25-pin serial port (DB25), while the short distance communication (< 12m), power cables can be connected directly to standard RS232 port (RS422, RS485 far), if the distance over far, the need to attach a modem (MODEM). The most simple and commonly used is a three-wire connection, that is, the receive data and send data tripod connected, this only involves the most basic connection, and directly connected with RS232 to answer the front-end consulting friends