diff --git a/src/iperf.h b/src/iperf.h
index 4043031b3..cb2807a6f 100644
--- a/src/iperf.h
+++ b/src/iperf.h
@@ -343,6 +343,8 @@ struct iperf_test
     int	      verbose;                          /* -V option - verbose mode */
     int	      json_output;                      /* -J option - JSON output */
     int	      json_stream;                      /* --json-stream */
+    void      (*json_callback) (struct iperf_test *, char *); /* allow user apps to receive the
+                                                JSON strings,instead of writing them to the output file */
     int	      zerocopy;                         /* -Z option - use sendfile */
     int       debug;				/* -d option - enable debug */
     enum      debug_level debug_level;          /* -d option option - level of debug messages to show */
diff --git a/src/iperf_api.c b/src/iperf_api.c
index cae4332a2..6fbd79f84 100644
--- a/src/iperf_api.c
+++ b/src/iperf_api.c
@@ -697,6 +697,12 @@ iperf_set_test_json_stream(struct iperf_test *ipt, int json_stream)
     ipt->json_stream = json_stream;
 }
 
+void
+iperf_set_test_json_callback(struct iperf_test *ipt, void (*callback)(struct iperf_test *, char *))
+{
+    ipt->json_callback = callback;
+}
+
 int
 iperf_has_zerocopy( void )
 {
@@ -2864,12 +2870,16 @@ JSONStream_Output(struct iperf_test * test, const char * event_name, cJSON * obj
     char *str = cJSON_PrintUnformatted(event);
     if (str == NULL)
         return -1;
-    if (pthread_mutex_lock(&(test->print_mutex)) != 0) {
-        perror("iperf_json_finish: pthread_mutex_lock");
-    }
-    fprintf(test->outfile, "%s\n", str);
-    if (pthread_mutex_unlock(&(test->print_mutex)) != 0) {
-        perror("iperf_json_finish: pthread_mutex_unlock");
+    if (test->json_callback != NULL) {
+        (test->json_callback)(test, str);
+    } else {
+        if (pthread_mutex_lock(&(test->print_mutex)) != 0) {
+            perror("iperf_json_finish: pthread_mutex_lock");
+        }
+        fprintf(test->outfile, "%s\n", str);
+        if (pthread_mutex_unlock(&(test->print_mutex)) != 0) {
+            perror("iperf_json_finish: pthread_mutex_unlock");
+        }
     }
     iflush(test);
     cJSON_free(str);
@@ -3060,6 +3070,8 @@ iperf_defaults(struct iperf_test *testp)
     testp->settings->rcv_timeout.usecs = (DEFAULT_NO_MSG_RCVD_TIMEOUT % SEC_TO_mS) * mS_TO_US;
     testp->zerocopy = 0;
 
+    testp->json_callback = NULL;
+
     memset(testp->cookie, 0, COOKIE_SIZE);
 
     testp->multisend = 10;	/* arbitrary */
@@ -5035,14 +5047,18 @@ iperf_json_finish(struct iperf_test *test)
             if (test->json_output_string == NULL) {
                 return -1;
             }
-            if (pthread_mutex_lock(&(test->print_mutex)) != 0) {
-                perror("iperf_json_finish: pthread_mutex_lock");
-            }
-            fprintf(test->outfile, "%s\n", test->json_output_string);
-            if (pthread_mutex_unlock(&(test->print_mutex)) != 0) {
-                perror("iperf_json_finish: pthread_mutex_unlock");
+            if (test->json_callback != NULL) {
+                (test->json_callback)(test, test->json_output_string);
+            } else {
+                if (pthread_mutex_lock(&(test->print_mutex)) != 0) {
+                    perror("iperf_json_finish: pthread_mutex_lock");
+                }
+                fprintf(test->outfile, "%s\n", test->json_output_string);
+                if (pthread_mutex_unlock(&(test->print_mutex)) != 0) {
+                    perror("iperf_json_finish: pthread_mutex_unlock");
+                }
+                iflush(test);
             }
-            iflush(test);
         }
         cJSON_Delete(test->json_top);
     }
diff --git a/src/iperf_api.h b/src/iperf_api.h
index 2b71613e9..471cc9032 100644
--- a/src/iperf_api.h
+++ b/src/iperf_api.h
@@ -197,6 +197,7 @@ void    iperf_set_test_template( struct iperf_test *ipt, const char *tmp_templat
 void	iperf_set_test_reverse( struct iperf_test* ipt, int reverse );
 void	iperf_set_test_json_output( struct iperf_test* ipt, int json_output );
 void	iperf_set_test_json_stream( struct iperf_test* ipt, int json_stream );
+void    iperf_set_test_json_callback(struct iperf_test *ipt, void (*callback)(struct iperf_test *, char *));
 int	iperf_has_zerocopy( void );
 void	iperf_set_test_zerocopy( struct iperf_test* ipt, int zerocopy );
 void	iperf_set_test_get_server_output( struct iperf_test* ipt, int get_server_output );
@@ -419,7 +420,7 @@ enum {
     IERVRSONLYRCVTIMEOUT = 32,  // Client receive timeout is valid only in reverse mode
     IESNDTIMEOUT = 33,      // Illegal message send timeout
     IEUDPFILETRANSFER = 34, // Cannot transfer file using UDP
-    IESERVERAUTHUSERS = 35,   // Cannot access authorized users file
+    IESERVERAUTHUSERS = 35,  // Cannot access authorized users file
     /* Test errors */
     IENEWTEST = 100,        // Unable to create a new test (check perror)
     IEINITTEST = 101,       // Test initialization failed (check perror)