Quectel EC25 Sending SMS and getting +CMS ERROR 305

This code sends some of SMS messages. But it gives error for some of the messages. It may about some wrong character that GSM module does not recognize like `(. Is there any one can help to fix the code. I am checking if GSM device is attached to ttyUSB2. This is C++ code.

int sendSms(UsbPort &device, string phoneNumber, string message) {

    char buf[MAXBUF] = {0};
    int n;

    if(device.fildes > 0) {
        int max_check = 0;

        if (write(device.fildes, "ATZ\r", 4) < 4) {
            printf("ATZ write error - %s \n", strerror(errno));
            return -1;
        }

        this_thread::sleep_for(chrono::seconds(1));

        if (write(device.fildes, "AT+CMGF=1\r", 10) < 10) {
            printf("AT+CMGF=1 write error - %s \n", strerror(errno));
            return -1;
        }

        if (tcdrain(device.fildes) != 0) {
            perror("tcdrain() error");
            return -1;
        }

        this_thread::sleep_for(chrono::seconds(1));
        bzero(buf, sizeof(buf));
        read(device.fildes, buf, MAXBUF - 1);
        cout << "Buffer-1 = " << buf << endl;

        if (write(device.fildes, "ATE+CSMS=1\r", 11) < 11) {
            printf("ATE+CSMS=1 write error - %s \n", strerror(errno));
            return -1;
        }

        if (tcdrain(device.fildes) != 0) {
            perror("tcdrain() error");
            return -1;
        }

        this_thread::sleep_for(chrono::seconds(1));
        bzero(buf, sizeof(buf));

        if ((n = read(device.fildes, buf, MAXBUF - 1)) > -1) {
            int length = strlen(buf);
            cout << "length = " << length << endl;
            buf[length] = '\0';
            cout << "Buffer-2 = " << buf << endl;
            if (strstr(buf, "+CSMS:") != NULL) { // Ready to send SMS
                cout << "Can send SMS: " + string(buf) << endl;
                // Send SMS
                string data1 = "AT+CMGS=\"" + phoneNumber + "\"\r";
                if (write(device.fildes, data1.c_str(), data1.length()) < data1.length()) {
                    printf("AT+CMGS write error - %s \n", strerror(errno));
                    return -1;
                }
                else {
                    this_thread::sleep_for(chrono::seconds(1));
                    string data2 = message + "\x1A";
                    if (write(device.fildes, data2.c_str(), data2.length()) < data2.length()) {
                        printf("ATE+CSMS=1 write error - %s \n", strerror(errno));
                        return -1;
                    }

                    if (tcdrain(device.fildes) != 0) {
                        perror("tcdrain() error");
                        return -1;
                    }

                    this_thread::sleep_for(chrono::seconds(1));
                    bzero(buf, sizeof(buf));
                    if ((n = read(device.fildes, buf, MAXBUF - 1)) > -1) {
                        int length = strlen(buf);
                        cout << "length = " << length << endl;
                        buf[length] = '\0';
                        cout << "Buffer-2 = " << buf << endl;
                        if (strstr(buf, "OK") != NULL) {
                            cout << message + " sent to : " + telNo + " successfully." << endl;
                            return 0;
                        }
                    }
                    else {
                        cout << message + " sent to : " + telNo + " unsuccessful!" << endl;
                        return -1;
                    }
                }
            }
            else {
                cout << "Error: buf = " + string(buf) << endl;
                return -1;
            }
        }
    }
    return -1;
}

this is the example of which it cannot send sms.

Solution

The problem was not about ASCII characters, but about sending a message longer than it should be.

When we use Concatenated SMS it solved our problem. It Send Sms without problem.

AT+CGMF=1
AT+CSCS="GSM"
AT+CSMP=17,167,0,241
AT+CMGS="Number"
> Message <CTRL+Z>