Serial communication

Hello! I'm not sure if this goes here because is my first thread. I have a problem with some program that tries to send and receive info through serial port (virtual). I need to send 2 commands and I can do it properly but then I need to read info buf the program gets blocked... The code is here Code: #include <stdio.h> // standard input / output functions #include <string.h> // string function definitions #include <unistd.h> // UNIX standard function definitions #include <fcntl.h> // File control definitions #include <errno.h> // Error number definitions #include <termios.h> // POSIX terminal control definitionss #include <time.h>  // time calls int open_port(void) {         int fd; // file description for the serial port         fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY);         return(fd); } int configure_port(int fd)      // configure the port {         struct termios port_settings;      // structure to store the port settings in         cfsetispeed(&port_settings, B19200);    // set baud rates         cfsetospeed(&port_settings, B19200);         port_settings.c_cflag &= ~PARENB;    // set no parity         port_settings.c_cflag &= CSTOPB;    // 2 stop bytes         port_settings.c_cflag &= CREAD;         port_settings.c_cflag &= CLOCAL;         port_settings.c_cflag &= ~CSIZE;    //8 bites of data         port_settings.c_cflag |= CS8;              tcsetattr(fd, TCSANOW, &port_settings);    // apply the settings to the port NOW         return(fd); } int read_info(int fd)  // query modem with an AT command {         char datos[10];         char command = 0x53, address=0x52,size=0x07;         sprintf(datos,"%c%c%c", command,address,0x57);         write(fd,datos,3);         sleep(1);         printf("Frist write issued");         command = 0x54, address=0x53;         sprintf(datos,"%c%c%c", command,address,size);         write(fd,datos,3);         printf("Second write issued");         int rd = read(fd,datos,7);//Here is the trouble!         int i;         for(i=0;i<10;i++) {printf("Datos[%d]: %c\n",i,datos[i]);} } int main(void) {         int fd = open_port();         configure_port(fd);         printf("PORT PREPARED!\n");         read_info(fd);         return(0); } I hope somebody can tell me what I'm doing wrong... and I have to say that the writing was okey so the parameters seem to be right too.

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