LinuxQuestions.org - xTerm on pseudo terminal hast no output

Hello,
I hope this is the right forum for my issue.
I'm writing a programm in c++ and want a interactiv way to communicate with it. The program opens a pseudo terminal(pt) in read/write mode and after that it forcs and opens a xTerm instance with the -Sccn option.
After playing around with the ps options like ICANON and ECHO I got a running example in raw mode but then I have to implement the line discipline and the erasing characters an so on on my self.
I don't want to do this :-)
What I want is to get a Xterm/pt connection to my application where only line will be transmitted and signals and erase chars are processed.
At this time. I have following situation:
Turned ICANON on.
My applications sends a couple of chars to the pt-master (ptm). Nothing will be printed on the xTerm.
If I type some chars into the xTerm window, my application receives them. (char after char ... no CR or else) The chars I typed not even printed in the xTerm window.
If nothing is to read the read() funktion returns -1.

Here are the code of the opening and configurating the pt.

Code:

                tty_master_fd = open ("/dev/ptmx", O_RDWR | O_NOCTTY| O_NDELAY); //open Master for pseudo terminal

                grantpt(tty_master_fd);                                                //necessary for pseudo terminal, grant the new terminal the right of the opening process

                unlockpt(tty_master_fd);                                        //necessary for pseudo terminal, unlocks the terminal so other programs can read/write to it

                tty_slavename = ptsname(tty_master_fd);                //read path for slave side of the pseudo terminal

                int tty_slave_fd = open(tty_slavename, O_RDWR | O_NOCTTY | O_NDELAY);        //open slave side of the terminal

...

                struct termios termInfo;                                                //create new register set

                tcgetattr(tty_slave_fd, &termInfo);

                termInfo.c_lflag &= ~(ECHOPRT);                                                

                termInfo.c_lflag |= (ICANON | ECHO | ECHOE | ECHOKE | ECHONL | CLOCAL );

                termInfo.c_oflag |= ONLRET;                                                //transform new line characters to carriage return



                tcsetattr( tty_slave_fd, TCSANOW, &termInfo );        //set changes to the control registers now

                tcsetattr(tty_master_fd, TCSANOW, &termInfo );        // don't know whitch side of the pt  I have to control

...

                int terminal= fork();

                if(terminal==0)

                {

                        //cout<<args<<endl;        //for debug

                        termPID = execvp("xterm",arg);        //start the xterm

                }

I hope somebody can give me a hint where my error is.