Libserial, read serial port

[helma]

I am using libserial library to interact with a modem using c++. The C++ code sends an AT command:

my_serial_stream << "AT+CSQ" << '\r' ;

The modem responds with a response, either ERROR or OK,

The c++ code to read the response:

while( serial_port.rdbuf()->in_avail() > 0 )
{
    char next_byte;
    serial_port.get(next_byte);
    std::cerr << std::hex << (int)next_byte << " ";
}
std::cerr << std::endl;

i would like to handle the response such that if the response is OK, the modem sends another command and if the response is ERROR, the modem resends the first command.