diff --git a/include/neuron/connection/neu_connection.h b/include/neuron/connection/neu_connection.h
index cce6b69b..cbdc1950 100644
--- a/include/neuron/connection/neu_connection.h
+++ b/include/neuron/connection/neu_connection.h
@@ -43,6 +43,9 @@ typedef enum neu_conn_tty_baud {
     NEU_CONN_TTY_BAUD_1800,
     NEU_CONN_TTY_BAUD_1200,
     NEU_CONN_TTY_BAUD_600,
+    NEU_CONN_TTY_BAUD_300,
+    NEU_CONN_TTY_BAUD_200,
+    NEU_CONN_TTY_BAUD_150,
 } neu_conn_tty_baud_e;
 
 typedef enum neu_conn_tty_parity {
diff --git a/src/connection/connection.c b/src/connection/connection.c
index cec4cd90..ca098f97 100644
--- a/src/connection/connection.c
+++ b/src/connection/connection.c
@@ -69,6 +69,8 @@ struct neu_conn {
 static void conn_tcp_server_add_client(neu_conn_t *conn, int fd,
                                        struct sockaddr_in client);
 static void conn_tcp_server_del_client(neu_conn_t *conn, int fd);
+static int  conn_tcp_server_replace_client(neu_conn_t *conn, int fd,
+                                           struct sockaddr_in client);
 
 static void conn_tcp_server_listen(neu_conn_t *conn);
 static void conn_tcp_server_stop(neu_conn_t *conn);
@@ -180,16 +182,6 @@ int neu_conn_tcp_server_accept(neu_conn_t *conn)
         return -1;
     }
 
-    if (conn->tcp_server.n_client >= conn->param.params.tcp_server.max_link) {
-        close(fd);
-        zlog_warn(conn->param.log, "%s:%d accpet max link: %d, reject",
-                  conn->param.params.tcp_server.ip,
-                  conn->param.params.tcp_server.port,
-                  conn->param.params.tcp_server.max_link);
-        pthread_mutex_unlock(&conn->mtx);
-        return -1;
-    }
-
     if (conn->block) {
         struct timeval tv = {
             .tv_sec  = conn->param.params.tcp_server.timeout / 1000,
@@ -199,7 +191,23 @@ int neu_conn_tcp_server_accept(neu_conn_t *conn)
         setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
     }
 
-    conn_tcp_server_add_client(conn, fd, client);
+    if (conn->tcp_server.n_client >= conn->param.params.tcp_server.max_link) {
+        int free_fd = conn_tcp_server_replace_client(conn, fd, client);
+        if (free_fd > 0) {
+            zlog_warn(conn->param.log, "replace old client %d with %d", free_fd,
+                      fd);
+        } else {
+            close(fd);
+            zlog_warn(conn->param.log, "%s:%d accpet max link: %d, reject",
+                      conn->param.params.tcp_server.ip,
+                      conn->param.params.tcp_server.port,
+                      conn->param.params.tcp_server.max_link);
+            pthread_mutex_unlock(&conn->mtx);
+            return -1;
+        }
+    } else {
+        conn_tcp_server_add_client(conn, fd, client);
+    }
 
     conn->is_connected = true;
     conn->connected(conn->data, fd);
@@ -740,6 +748,18 @@ static void conn_connect(neu_conn_t *conn)
             cfsetospeed(&tty_opt, B600);
             cfsetispeed(&tty_opt, B600);
             break;
+        case NEU_CONN_TTY_BAUD_300:
+            cfsetospeed(&tty_opt, B300);
+            cfsetispeed(&tty_opt, B300);
+            break;
+        case NEU_CONN_TTY_BAUD_200:
+            cfsetospeed(&tty_opt, B200);
+            cfsetispeed(&tty_opt, B200);
+            break;
+        case NEU_CONN_TTY_BAUD_150:
+            cfsetospeed(&tty_opt, B150);
+            cfsetispeed(&tty_opt, B150);
+            break;
         }
 
         switch (conn->param.params.tty_client.parity) {
@@ -879,6 +899,25 @@ static void conn_tcp_server_del_client(neu_conn_t *conn, int fd)
     }
 }
 
+static int conn_tcp_server_replace_client(neu_conn_t *conn, int fd,
+                                          struct sockaddr_in client)
+{
+    for (int i = 0; i < conn->param.params.tcp_server.max_link; i++) {
+        if (conn->tcp_server.clients[i].fd > 0) {
+            int ret = conn->tcp_server.clients[i].fd;
+
+            close(conn->tcp_server.clients[i].fd);
+            conn->tcp_server.clients[i].fd = 0;
+
+            conn->tcp_server.clients[i].fd     = fd;
+            conn->tcp_server.clients[i].client = client;
+            return ret;
+        }
+    }
+
+    return 0;
+}
+
 int neu_conn_stream_consume(neu_conn_t *conn, void *context,
                             neu_conn_stream_consume_fn fn)
 {