Up and down serial test

//1.3. AT Command Responses
//When the AT command processor has finished processing a line, it will output "OK" or "ERROR" or “+CME ERROR:<err>” indicating that it is ready to accept a new command. Solicited informational responses are sent before the final "OK" or "ERROR" or “+CME ERROR:<err>”.
//Responses will be of the format:
//<CR><LF>+CMD1:<parameters><CR><LF> <CR><LF>OK<CR><LF>
//Or
//<CR><LF><parameters><CR><LF> <CR><LF>OK<CR><LF>
//
//
// Sample form Serial Monitor
//
// OK
//
// If there is any error, response:
// ERROR
// Or
// +CME ERROR:<err>
//

#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11);

char chrIMEI[16];
char serialdata[256]; //Array to store the chars before parsing, size???

int readline(int readch, char *buffer, int len) {
  static int pos = 0;
  int rpos;
  if (readch > 0) {
    switch (readch) {
      case '\r': // Ignore CR
        break;
      case '\n': // Return on new-line
        rpos = pos;
        pos = 0;  // Reset position index ready for next time
        return rpos;
      default:
        if (pos < len - 1) {
          buffer[pos++] = readch;
          buffer[pos] = 0;
        }
        break;
    }
  }
  return 0;
}

void setSocket() {
  mySerial.write("AT+NSOCR=DGRAM,17,7000,1\r\n");
}

void setup() {
  Serial.begin(9600);
  while (!Serial) {
  }
  Serial.println("Testing up- and downlink");
  mySerial.begin(9600);
  //setSocket(); // Only on power cycle, not after reflashing..?
}

void loop() {
  // Open socket first after power cycle: AT+NSOCR=DGRAM,17,7000,1\r\n
  // Send "Hello World", 11=length
  // AT+NSOST=0,999.99.999.999,99999,11,48656c6c6f20576f726c64

  if (mySerial.available()) {
    if (readline(mySerial.read(), serialdata, 512)) {
      // Command: AT+CGSN=1
      // Response: +CGSN:999999999999999
      if (strncmp(serialdata, "+CGSN:", 6) == 0) {
        for (int i = 0; i < 16; i++) {
          chrIMEI[i] = serialdata[6 + i];
        }
        chrIMEI[15] = '\0';
      }

      // +NSONMI  Indicator of Arrived Socket Messages (Response Only)
      // Message: "Hello"
      // Response: +NSONMI:0,5 (<socket>,<length>)
      // Command to download: AT+NSORF=0,5 <socket>,<req_length>
      // Response <socket>,<ip_addr>,<port>,<length>,<data>,<remaining_ length>
      // Example: 0,999.99.999.999,99999,5,48656C6C6F,0
      if (strncmp(serialdata, "+NSONMI:", 8) == 0) {
        char *csocket = strtok(serialdata + 8, ":");
        char *cbytes = strtok(NULL, ",");
        // Check the last slicing worked
        if (cbytes != NULL) {
          int socket = atoi(csocket);
          int bytes = atoi(cbytes);
        }
        // Proceed and download messages here?
      }
    }
  }
}