fix: read might return -1

Author: robert-burger

src/esl.cpp

@@ -247,7 +247,9 @@ void esl::run(void) {
         // receive from socket
         size_t bytesrx = dev_stream->read(&recv_buffer[0], ESL_PREFIX_SIZE + MAX_MTU);
 
-        if (bytesrx > (int)ESL_PREFIX_SIZE) {
+        if ((ssize_t)bytesrx == -1) {
+            continue;
+        } else if (bytesrx > (int)ESL_PREFIX_SIZE) {
             if (memcmp(recv_buffer, recv_mac_id, 6) == 0) {
                 struct esl_prefix *prefix = (struct esl_prefix *)&recv_buffer[0];
                 int no = get_port_no(prefix->ctrl_state & ESL__CTRL_STATE__PORT_MASK);