diff --git a/src/source-test.c b/src/source-test.c
index 42c17ff..898ca32 100644
--- a/src/source-test.c
+++ b/src/source-test.c
@@ -19,6 +19,7 @@ int main(int argc, char *argv[]) {
   f2b_config_section_t *section = NULL;
   f2b_source_t         *source  = NULL;
   char buf[1024] = "";
+  uint32_t stag;
   bool reset;
 
   if (argc < 3)
@@ -54,9 +55,9 @@ int main(int argc, char *argv[]) {
 
   while (1) {
     reset = true;
-    while (f2b_source_next(source, buf, sizeof(buf), reset)) {
+    while ((stag = f2b_source_next(source, buf, sizeof(buf), reset)) > 0) {
       reset = false;
-      puts(buf);
+      printf("stag: %08X, line: %s\n", stag, buf);
     }
     sleep(1);
   }
diff --git a/src/source.c b/src/source.c
index e0402da..8a74bff 100644
--- a/src/source.c
+++ b/src/source.c
@@ -122,7 +122,7 @@ f2b_source_destroy(f2b_source_t *source) {
   free(source);
 }
 
-bool
+uint32_t
 f2b_source_next(f2b_source_t *source, char *buf, size_t bufsize, bool reset) {
   assert(source != NULL);
   return source->next(source->cfg, buf, bufsize, reset);
diff --git a/src/source.h b/src/source.h
index a084dfa..d08e4e5 100644
--- a/src/source.h
+++ b/src/source.h
@@ -29,7 +29,7 @@ typedef struct f2b_source_t {
   /** dlsym pointer to handler of @a start command */
   bool  (*start)   (void *cfg);
   /** dlsym pointer to handler of @a next command */
-  bool  (*next)    (void *cfg, char *buf, size_t bufsize, bool reset);
+  uint32_t (*next) (void *cfg, char *buf, size_t bufsize, bool reset);
   /** dlsym pointer to handler of @a stats command */
   bool  (*stats)   (void *cfg, char *buf, size_t bufsize);
   /** dlsym pointer to handler of @a stop command */
@@ -74,9 +74,9 @@ bool f2b_source_start (f2b_source_t *s);
  * @param buf Buffer for data
  * @param bufsize Size of buffer for data
  * @param reset Reset source internals
- * @returns false of no data available, true otherwise with setting @a buf
+ * @returns >0 on new data available with filling @a buf and 0 on no data/error
  */
-bool f2b_source_next (f2b_source_t *s, char *buf, size_t bufsize, bool reset);
+uint32_t f2b_source_next (f2b_source_t *s, char *buf, size_t bufsize, bool reset);
 /**
  * @brief Stop given source
  * @param s Pointer to source struct
diff --git a/src/sources/files.c b/src/sources/files.c
index 52ccbff..0490f91 100644
--- a/src/sources/files.c
+++ b/src/sources/files.c
@@ -196,7 +196,7 @@ stop(cfg_t *cfg) {
   return true;
 }
 
-bool
+uint32_t
 next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
   assert(cfg != NULL);
   assert(buf != NULL);
@@ -213,10 +213,10 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
       continue;
     }
     if (file_getline(file, buf, bufsize))
-      return true;
+      return file->stag;
   }
 
-  return false;
+  return 0;
 }
 
 bool
diff --git a/src/sources/portknock.c b/src/sources/portknock.c
index 33d15b9..06d01f0 100644
--- a/src/sources/portknock.c
+++ b/src/sources/portknock.c
@@ -163,7 +163,7 @@ stop(cfg_t *cfg) {
   return true;
 }
 
-bool
+uint32_t
 next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
   struct sockaddr_storage addr;
   socklen_t addrlen;
@@ -191,16 +191,16 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
     close(sock);
     if (addr.ss_family == AF_INET) {
       inet_ntop(AF_INET,  &(((struct sockaddr_in *) &addr)->sin_addr), buf, bufsize);
-      return true;
+      return port->stag;
     }
     if (addr.ss_family == AF_INET6) {
       inet_ntop(AF_INET6, &(((struct sockaddr_in6 *) &addr)->sin6_addr), buf, bufsize);
-      return true;
+      return port->stag;
     }
     cfg->logcb(error, "can't convert sockaddr to string: unknown AF");
   }
 
-  return false;
+  return 0;
 }
 
 bool
diff --git a/src/sources/redis.c b/src/sources/redis.c
index 49d7215..09b754e 100644
--- a/src/sources/redis.c
+++ b/src/sources/redis.c
@@ -168,9 +168,9 @@ stop(cfg_t *cfg) {
   return true;
 }
 
-bool
+uint32_t
 next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
-  bool gotit = false;
+  uint32_t res = 0;
   assert(cfg != NULL);
   assert(buf != NULL);
   assert(bufsize > 0);
@@ -180,11 +180,11 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
   if (!cfg->conn || cfg->conn->err)
     redis_connect(cfg);
   if (!cfg->conn)
-    return false; /* reconnect failure */
+    return 0; /* reconnect failure */
 
   if (cfg->conn->err) {
     log_msg(cfg, error, "connection error: %s", cfg->conn->errstr);
-    return false;
+    return 0;
   }
 
   redisReply *reply = NULL;
@@ -194,7 +194,7 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
       if (strcmp(reply->element[0]->str, "message") == 0 ||
           strcmp(reply->element[1]->str, cfg->hash) == 0) {
         strlcpy(buf, reply->element[2]->str, bufsize);
-        gotit = true;
+        res = (uint32_t) -1;
       } else {
         log_msg(cfg, error, "wrong redis message type: %s", reply->element[0]->str);
       }
@@ -208,7 +208,7 @@ next(cfg_t *cfg, char *buf, size_t bufsize, bool reset) {
     log_msg(cfg, error, "can't get reply from server %s: %s", cfg->host, cfg->conn->errstr);
   }
 
-  return gotit;
+  return res;
 }
 
 bool
diff --git a/src/sources/source.h b/src/sources/source.h
index 806addc..84b5a2e 100644
--- a/src/sources/source.h
+++ b/src/sources/source.h
@@ -77,7 +77,7 @@ extern bool    start(cfg_t *cfg);
  * @param reset Reset internals to start of list
  * @returns false if no new data available, or true otherwise with filling @a buf
  */
-extern bool     next(cfg_t *cfg, char *buf, size_t bufsize, bool reset);
+extern uint32_t next(cfg_t *cfg, char *buf, size_t bufsize, bool reset);
 /**
  * @brief Get statistics for source
  * @param cfg Module handler