//手机号码转换为pdu模式
        private string telc(string MobileNum)
        {
            int tl;
            string ltem, rtem, ttem;
            int ti;

            ttem = "";
            tl = MobileNum.Trim().Length;
            if (tl != 11 && tl != 13)
            {
                MessageBox.Show("wrong number:" + MobileNum);
                return "";
            }

            if (tl == 11)  // 11位转换为13位
            {
                tl += 2;
                MobileNum = "86" + MobileNum;
            }

            for (ti = 0; ti < tl; ti += 2)
            {
                ltem = MobileNum.Substring(ti, 1);
                if (ti == tl - 1)
                {
                    rtem = "F";
                }
                else
                {
                    rtem = MobileNum.Substring(ti + 1, 1);
                }

                ttem += rtem + ltem;  //每两位颠倒
            }

            return ttem;
        }

//Unicode解码函数
        private string ascg(string smsg)
        {
            string res="";
            string ls;
            string rs;

            byte[] resByte = System.Text.UnicodeEncoding.Unicode.GetBytes(smsg);
            for (int i = 0; i < resByte.Length ; i+=2)
            {
                ls = resByte[i].ToString("X2");
                rs = resByte[i + 1].ToString("X2");
                res = res + rs + ls; //注意这里高低位颠倒
            }
            return res.Trim();
        }

private void SendSMS(string csca,string num, string msg)
        {
            string prex = "0891";
            string midx = "11000D91";
            string sufx = "000800";

            string pdu, psmsc, pnum, pmsg;
            string leng;
            int length;
            if (!sp.IsOpen)
            {
                sp.Open();
            }

            length = (msg.Length) * 2;
            leng = length.ToString("X");

            if (length < 16)
            {
                leng = "0" + leng;
            }

            psmsc = telc(csca).Trim();
            pnum = telc(num).Trim();
            pmsg = ascg(msg.Trim());
            pdu = prex + psmsc + midx + pnum + sufx + leng + pmsg;//注意编码组合方式

            sp.WriteLine("AT+CMGF=0\r");
            sp.WriteLine("AT+CMGS=" + (15 + length).ToString() + "\r");

            byte[] end = { 0x1a };
            sp.WriteLine(pdu + System.Text.ASCIIEncoding.ASCII.GetString(end));
        }