Fix reference example in README (#18)

README.md

@@ -20,13 +20,14 @@ See memory requirements for this library [here](https://docs.aws.amazon.com/embe
 
 ## Reference example
 
-The example below shows how to use the backoffAlgorithm library to retry a DNS resolution query for `amazon.com`.
+The example below shows how to use the backoffAlgorithm library on a POSIX platform to retry a DNS resolution query for `amazon.com`.
 
 ```c
 #include "backoff_algorithm.h"
 #include <stdlib.h>
 #include <string.h>
 #include <netdb.h>
+#include <unistd.h>
 #include <time.h>
 
 /* The maximum number of retries for the example code. */
@@ -44,11 +45,11 @@ int main()
  BackoffAlgorithmStatus_t retryStatus = BackoffAlgorithmSuccess;
  BackoffAlgorithmContext_t retryParams;
  char serverAddress[] = "amazon.com";
- uint16_t nextRetryBackOff = 0;
+ uint16_t nextRetryBackoff = 0;
 
  int32_t dnsStatus = -1;
  struct addrinfo hints;
- struct addrinfo ** pListHead;
+ struct addrinfo ** pListHead = NULL;
  struct timespec tp;
 
  /* Add hints to retrieve only TCP sockets in getaddrinfo. */
@@ -86,12 +87,19 @@ int main()
   {
   /* Generate a random number and get back-off value (in milliseconds) for the next retry.
   * Note: It is recommended to use a random number generator that is seeded with
-  * device-specific entropy source so that backoff calculation in devices is different 
+  * device-specific entropy source so that backoff calculation across devices is different
   * and possibility of network collision between devices attempting retries can be avoided.
   *
-  * For the simplicity of the code example, the pseudo random number generator, rand() function
-  * is used. */
-  retryStatus = BackoffAlgorithm_GetNextBackoff( &retryParams, rand(), &nextRetryBackOff );
+  * For the simplicity of this code example, the pseudo random number generator, rand()
+  * function is used. */
+  retryStatus = BackoffAlgorithm_GetNextBackoff( &retryParams, rand(), &nextRetryBackoff );
+
+  /* Wait for the calculated backoff period before the next retry attempt of querying DNS.
+  * As usleep() takes nanoseconds as the parameter, we multiply the backoff period by 1000. */
+  ( void ) usleep( nextRetryBackoff * 1000U );
+
+  /* Retry the DNS lookup for the host name. */
+  dnsStatus = getaddrinfo( serverAddress, NULL, &hints, pListHead );
   }
  } while( ( dnsStatus != 0 ) && ( retryStatus != BackoffAlgorithmRetriesExhausted ) );