什么是面向字符型协议? ---- 以字符为控制传输信息的基本单元; ASIIC码: 格式字符:SOH (start of heading) STX (start of text) ETB (end of transmission block) ETX (end of text) 控制字符:ACK (acknoledge) NAK (negative acknoledge) ENQ (enquire) EOT (end of transmission) SYN (synchrous) DLE (data link escape)