diff --git a/src/server.c b/src/server.c
index bc45229..33fadf1 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1618,6 +1618,13 @@ static int handle_sock(uint32_t key,
         goto done;
     }
 
+    /*
+     * NOTE: See AX.25 2.2, Section 6.4.1, "Sending I Frames"
+     */
+    if (sock->seq_recv + sock->n_window_tx == sock->seq_send) {
+        goto done;
+    }
+
     if ((len = read(sock->fd, sock->rx_buf, sock->n_maxlen_rx)) < 0) {
         if (errno == EIO) {
             (void)sock_shutdown(server, sock);