如何通过at命令使用GSM调制解调器发送和读取SMS

Question

我想使用带AT命令的gsm调制解调器发送和接收短信。我用作示例https://www.codeproject.com/Articles/38705/Send-and-Read-SMS-through-a-GSM-Modem-using-AT-Com？ 但是此程序发送消息<>，有时不发送消息。

port.PortName = "COM6";
port.ReadTimeout = 2000;
port.Open();
port.Write("AT" + "\r");
// Thread.Sleep(1500);
port.Write("AT+CMGF=1" + "\r");
Thread.Sleep(1500);
// port.Write("AT+CSCS=\"PCCP437\"" + "\r");
// Thread.Sleep(100);
port.Write("AT+CMGS=\"" + txtSIM.Text.Trim() + "\"" + "\r\n");
Thread.Sleep(1500);
port.Write(txtMessage.Text.Trim() + "\x1A");
MessageBox.Show("Message successfully");