Robotdyn uno r3 serial communication with esp, not working

Projects Networking, Protocols, and Devices
5

In uno

void serialEvent() {
  static int cmd=0;
  static String lstr="";
  static String subCmd="";
  while(Serial.available() > 0) {
    char inChar=(char)Serial.read();
    if (cmdIsSet) {
      if ((inChar == '\n') || (inChar == '\r')) {
        // cmd is set and subCmd is populated fully.
      } else
        subCmd+=inChar;
    } else
      lstr+=inChar;
      
    if (inChar == ':') {
      Serial.print("Received from esp - ");
      if (lstr.equalsIgnoreCase("MtrSpeed:"))
        cmd=CMD_MtrSpeed;
    if(cmd != 0)
    cmdIsSet=true;
    } else if ((inChar == '\n') || (inChar == '\r')) {
    if(cmdIsSet) {
    switch(cmd) {
    case CMD_MtrSpeed:
    {
      int sped=subCmd.toInt();
      analogWrite(mtrPin, sped);
      String resp=" MtrSpeed:"+subCmd;
      Serial.println(resp);
      loopSpeedSent=0;
      lstr="";
      subCmd="";
      cmdIsSet=0;
      cmd=0;
      break;
    }
  }
}

In esp

void findConfInSerial() {
  static String subCmd="";
  static int cmd=0;
  bool cmdIsSet=false;
  static String lstr="";
  while(Serial.available() > 0) {
    char inChar=(char)Serial.read();
  if (cmdIsSet) {
    if ((inChar == '\n') || (inChar == '\r')) {
      Log+=lstr+" : "+subCmd;
    } else
      subCmd+=inChar;
  if (inChar == ':') {
    Serial.print(" Received colon ");
    Serial.println(lstr);
      if (lstr.equalsIgnoreCase( "MtrSpeed:")) {
       String spd=Serial.readStringUntil('\n');
       respondSpeedReq(spd);
    }
}

The snippet is stripped out of my original code, since this is the section I am trying to unit test. Other wise the combined code runs to few hundreds of lines.