+void meshlink_set_channel_accept_cb(meshlink_handle_t *mesh, meshlink_channel_accept_cb_t cb) {
+ if(!mesh) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return;
+ }
+
+ pthread_mutex_lock(&mesh->mesh_mutex);
+ mesh->channel_accept_cb = cb;
+ mesh->receive_cb = channel_receive;
+
+ for splay_each(node_t, n, mesh->nodes) {
+ if(!n->utcp && n != mesh->self) {
+ n->utcp = utcp_init(channel_accept, channel_pre_accept, channel_send, n);
+ }
+ }
+
+ pthread_mutex_unlock(&mesh->mesh_mutex);
+}
+
+meshlink_channel_t *meshlink_channel_open_ex(meshlink_handle_t *mesh, meshlink_node_t *node, uint16_t port, meshlink_channel_receive_cb_t cb, const void *data, size_t len, uint32_t flags) {
+ if(data || len) {
+ abort(); // TODO: handle non-NULL data
+ }
+
+ if(!mesh || !node) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return NULL;
+ }
+
+ node_t *n = (node_t *)node;
+
+ if(!n->utcp) {
+ n->utcp = utcp_init(channel_accept, channel_pre_accept, channel_send, n);
+ mesh->receive_cb = channel_receive;
+
+ if(!n->utcp) {
+ meshlink_errno = errno == ENOMEM ? MESHLINK_ENOMEM : MESHLINK_EINTERNAL;
+ return NULL;
+ }
+ }
+
+ meshlink_channel_t *channel = xzalloc(sizeof(*channel));
+ channel->node = n;
+ channel->receive_cb = cb;
+ channel->c = utcp_connect_ex(n->utcp, port, channel_recv, channel, flags);
+
+ if(!channel->c) {
+ meshlink_errno = errno == ENOMEM ? MESHLINK_ENOMEM : MESHLINK_EINTERNAL;
+ free(channel);
+ return NULL;
+ }
+
+ return channel;
+}
+
+meshlink_channel_t *meshlink_channel_open(meshlink_handle_t *mesh, meshlink_node_t *node, uint16_t port, meshlink_channel_receive_cb_t cb, const void *data, size_t len) {
+ return meshlink_channel_open_ex(mesh, node, port, cb, data, len, MESHLINK_CHANNEL_TCP);
+}
+
+void meshlink_channel_shutdown(meshlink_handle_t *mesh, meshlink_channel_t *channel, int direction) {
+ if(!mesh || !channel) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return;
+ }
+
+ utcp_shutdown(channel->c, direction);
+}
+
+void meshlink_channel_close(meshlink_handle_t *mesh, meshlink_channel_t *channel) {
+ if(!mesh || !channel) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return;
+ }
+
+ utcp_close(channel->c);
+ free(channel);
+}
+
+ssize_t meshlink_channel_send(meshlink_handle_t *mesh, meshlink_channel_t *channel, const void *data, size_t len) {
+ if(!mesh || !channel) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return -1;
+ }
+
+ if(!len) {
+ return 0;
+ }
+
+ if(!data) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return -1;
+ }
+
+ // TODO: more finegrained locking.
+ // Ideally we want to put the data into the UTCP connection's send buffer.
+ // Then, preferrably only if there is room in the receiver window,
+ // kick the meshlink thread to go send packets.
+
+ pthread_mutex_lock(&mesh->mesh_mutex);
+ ssize_t retval = utcp_send(channel->c, data, len);
+ pthread_mutex_unlock(&mesh->mesh_mutex);
+
+ if(retval < 0) {
+ meshlink_errno = MESHLINK_ENETWORK;
+ }
+
+ return retval;
+}
+
+uint32_t meshlink_channel_get_flags(meshlink_handle_t *mesh, meshlink_channel_t *channel) {
+ if(!mesh || !channel) {
+ meshlink_errno = MESHLINK_EINVAL;
+ return -1;
+ }