c# - C - Serial port read byte different from sent byte -

i sending , receiving data between virtual serial ports created using com0com.

on 1 side c program running in ubuntu vm guest , other side c#.net program running on windows 10 host.

i can send , receive data between ttys ports on ubuntu , virtual com ports on windows, in simple test seems byte received in c program different send c# program.

byte sent c#.net: 0x4b

byte received in c: 0xb

notice missing '4', it's not typo mistake.

the question why byte different?

c code

#include <stdio.h> #include <fcntl.h> #include <termios.h> #include <sys/select.h> #include <time.h>  typedef unsigned char byte_t;  // *** function: open_port int open_port(char* tty_path){      int fd;     struct termios portsett;      printf("attempting open port: %s\n", tty_path);     fd = open(tty_path, o_rdwr | o_noctty | o_ndelay);      printf("file descriptor: %d\n", fd);      if(fd == -1){         printf("unable open port.\n");     } else {         printf("port open.\n");         fcntl(fd, f_setfl, 0);         printf("configuring port.\n");         cfsetispeed(&portsett, b115200);         cfsetospeed(&portsett, b115200);         portsett.c_cflag &= ~parenb;         portsett.c_cflag &= ~cstopb;         portsett.c_cflag &= ~csize;         portsett.c_cflag |= ~cs8;         tcsetattr(fd, tcsanow, &portsett);     }      return fd; }  / *** function: write_to_port int write_to_port(int fd){      //send single byte device should respond     byte_t commandbytes[1] = { 0x0 };      printf("attempting write serial port fd = %i.\n", fd);      int writeresult = write(fd, commandbytes, 1);     printf("write result: %i\n", writeresult);      return writeresult; }  / *** function: read_from_port int read_from_port(int fd){      byte_t readbuff[1];     int readresult = -1;      printf("attempting read serial port fd = %i.\n", fd);     readresult = read(fd, readbuff, sizeof(readbuff));     printf("read result: %d\n\n", readresult);          if(readresult >= 1)          printf("response: <0x%x>\n", readbuff[0]); //only expecting 1 byte response      return readresult; }  / *** function: main main() {     /* using virtual serial port pairs on host      read , write needs happen on different ttys */     char *tty_write_path = "/dev/ttys1";     char *tty_read_path = "/dev/ttys2";      int fd_write = open_port(tty_write_path);     int fd_read = open_port(tty_read_path);      write_to_port(fd_write);     usleep(2000000); //give time response arrive     read_from_port(fd_read);      if(close(fd_write) != 0)          printf("error closing file %i.\n", fd_write);     if(close(fd_read) != 0)          printf("error closing file %i.\n", fd_read); } 

c# code

using system.io.ports; serialport m_comportwrite = new serialport("com9", 115200, parity.none, 8); m_comportwrite.open();  byte[] commandbytes = new byte[] { 0x4b }; m_comportwrite.write(commandbytes , 0, commandbytes .length); 

seems set bits except cs8 here portsett.c_cflag |= ~cs8; should

portsett.c_cflag |= cs8; 

according other side settings (see 8)

serialport("com9", 115200, parity.none, 8);