static bool accept_cb(meshlink_handle_t *mesh, meshlink_channel_t *channel, uint16_t port, const void *data, size_t len) {
assert(port && port <= nchannels);
assert(!data);
static bool accept_cb(meshlink_handle_t *mesh, meshlink_channel_t *channel, uint16_t port, const void *data, size_t len) {
assert(port && port <= nchannels);
assert(!data);