update client and socket.c, add DNS support

GuoWenxue

2022-04-19 ea435789dc2fab30ec16fa765a0b6577fe08166a

 apue/1.File_IO/ds18b20.c

@@ -116,5 +116,7 @@
    /* convert string value to float value */
    *temp = atof(ptr)/1000;
   
    close(fd);

    return 0;
}