diff --git a/y_socket_t/include/y_socket_t/y_list_var_tool.h b/y_socket_t/include/y_socket_t/y_list_var_tool.h
index 0ec0893..4dbf923 100644
--- a/y_socket_t/include/y_socket_t/y_list_var_tool.h
+++ b/y_socket_t/include/y_socket_t/y_list_var_tool.h
@@ -41,4 +41,6 @@ size_t total_size_list_y_ptr_STRING(struct main_list_y_ptr_STRING *mstr);
 size_t copy_list_y_ptr_STRING_to_one_string(char **p_dst_str, struct main_list_y_ptr_STRING *mstr);
 struct main_list_y_ptr_STRING * split_str_to_main_list_y_ptr_STRING(char *str_org, char sep, size_t limit_size_str_org);
 
+void usage_cmdl();
+
 #endif /* Y_PTR_VAR_TOOL_H__C */
diff --git a/y_socket_t/src/y_socket_t/y_list_var_tool.c b/y_socket_t/src/y_socket_t/y_list_var_tool.c
index 95a4bb6..3e1a482 100644
--- a/y_socket_t/src/y_socket_t/y_list_var_tool.c
+++ b/y_socket_t/src/y_socket_t/y_list_var_tool.c
@@ -164,3 +164,22 @@ struct main_list_y_ptr_STRING * split_str_to_main_list_y_ptr_STRING(char *str_or
   return m_str;
 }
 
+void usage_cmdl(){
+  printf("usage:\n"
+  "sendto [addr] { \"cmd\" : \"[command]\" }\n"
+  "addr: ipv4 address or ipv6 address or all to send cmd to all nodes already in the list.\n"
+  "command: \n"
+  "\tupdate kill: to gracefully shutdown socket server.\n"
+  "\tupdate standby: to suspend all workers, but can receive all task but in queu tasks.\n"
+  "\tupdate wakeup: to wakeup all workers, and then execute all tasks in queu.\n"
+  "\tupdate remove node [addr]: to remove [addr] in the list.\n"
+  "\tupdate add node [addr]: to add [addr] in the list.\n"
+  "\tget file [filename]: to ask server to send file named [filename].\n"
+  "\t\tfilename can be absolute path or relative working directory path\n"
+  "\tpost file [filename] : to send file [filename] after header.\n"
+  "\t\tNeed to add \"seq\" and \"tm\" keys to have good handling, the payload is after the header {}\n"
+  "\t\tSee y_socket_send_file_for_node function.\n"
+  "\tpost ok [filenameid]: to acknowledge receipt [filename].\n"
+  "\t\t[filenameid] is to precise witch [filename] (file name from whom and when)\n"
+  );
+}
diff --git a/y_socket_t/src/y_socket_t/y_socket_t.c b/y_socket_t/src/y_socket_t/y_socket_t.c
index 2b6d833..3b20c4b 100644
--- a/y_socket_t/src/y_socket_t/y_socket_t.c
+++ b/y_socket_t/src/y_socket_t/y_socket_t.c
@@ -383,6 +383,7 @@ void handle_buf_socket_rec(struct main_list_y_ptr_HEADER_T *m_ok_head_l_t, struc
 }
 
 void *y_socket_poll_fds(void *arg){
+  usage_cmdl();
   struct y_socket_t * argSock = (struct y_socket_t*)arg;
 // // //
   struct main_list_ptr_y_WORKER_T * workers = create_var_list_ptr_y_WORKER_T();