diff --git a/HISTORY b/HISTORY
index a151414..155c536 100644
--- a/HISTORY
+++ b/HISTORY
@@ -1,6 +1,7 @@
 
-Version 1.65  2022-12-20
+Version 1.65  2022-12-30
   * locked_list.h: add functions locked_list_move and locked_list_move_tail
+  * add function tcp_socket_connected
 
 Version 1.64  2022-11-19
   * shared_func.[hc]: normalize_path use type string_t for general purpose
diff --git a/src/locked_list.h b/src/locked_list.h
index 3584942..dae110c 100644
--- a/src/locked_list.h
+++ b/src/locked_list.h
@@ -13,6 +13,9 @@ typedef struct fc_locked_list {
 extern "C" {
 #endif
 
+#define LOCKED_LIST_LOCK(list) PTHREAD_MUTEX_LOCK(&(list)->lock)
+#define LOCKED_LIST_UNLOCK(list) PTHREAD_MUTEX_UNLOCK(&(list)->lock)
+
     static inline int locked_list_init(FCLockedList *list)
     {
         int result;
diff --git a/src/sockopt.c b/src/sockopt.c
index 541d43c..6f02311 100644
--- a/src/sockopt.c
+++ b/src/sockopt.c
@@ -2690,3 +2690,36 @@ int fc_get_net_type_by_name(const char *net_type)
     }
 }
 
+bool tcp_socket_connected(int sock)
+{
+    socklen_t len;
+#if defined(OS_LINUX) || defined(OS_FREEBSD)
+
+#ifdef OS_LINUX
+    struct tcp_info info;
+#else
+#include <netinet/tcp_fsm.h>
+#define TCP_INFO         TCP_CONNECTION_INFO
+#define TCP_ESTABLISHED  TCPS_ESTABLISHED
+    struct tcp_connection_info info;
+#endif
+
+    len = sizeof(info);
+    if (getsockopt(sock, IPPROTO_TCP, TCP_INFO, &info, &len) < 0) {
+        return false;
+    }
+    if (info.tcpi_state == TCP_ESTABLISHED) {
+        return true;
+    } else {
+        return false;
+    }
+#else
+	int result;
+    len = sizeof(result);
+    if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &result, &len) < 0) {
+        return false;
+    } else {
+        return (result == 0);
+    }
+#endif
+}
diff --git a/src/sockopt.h b/src/sockopt.h
index 6418e47..bd1ea37 100644
--- a/src/sockopt.h
+++ b/src/sockopt.h
@@ -702,6 +702,8 @@ static inline void tcp_dont_try_again_when_interrupt()
 
 void tcp_set_quick_ack(const bool value);
 
+bool tcp_socket_connected(int sock);
+
 int fc_get_net_type_by_name(const char *net_type);
 
 int fc_get_net_type_by_ip(const char *ip);