*static void printErrorAndExit(const char* msg)
*static gboolean read_callback(GIOChannel *channel, GIOCondition cond, gpointer data)
*int createServerSocket()
*int createClientSocket(const char* host_name)
*void addGIOChannelToWidget(const int socket_fd, gpointer data)
*void exit_destructor(GtkWidget* widget, gpointer data)