patch 7.4.1262
Problem: The channel callback is not invoked.
Solution: Make a list of pending callbacks.
diff --git a/src/proto/channel.pro b/src/proto/channel.pro
index 197cddf..77040a5 100644
--- a/src/proto/channel.pro
+++ b/src/proto/channel.pro
@@ -3,7 +3,7 @@
int channel_open(char *hostname, int port_in, void (*close_cb)(void));
void channel_set_json_mode(int idx, int json_mode);
void channel_set_callback(int idx, char_u *callback);
-void channel_set_req_callback(int idx, char_u *callback);
+void channel_set_req_callback(int idx, char_u *callback, int id);
char_u *channel_get(int idx);
int channel_collapse(int idx);
int channel_is_open(int idx);