problem: router doesn't know when peer disconnected

ZMQ_ROUTER_NOTIFY doesn't have a context and doesn't play nice with protocols. with ZMQ_DISCONNECT_MSG we can set it to a protocol message, like DISCONNECT in majordomo. Router will send it when a peer is disconnected. Another advantage of ZMQ_DISCONNECT_MSG is that it also works on inproc.

Together with ZMQ_HEARTBEAT it allows to build very reliable protocols, and much simpler as well.

src/pipe.hpp

@@ -38,10 +38,10 @@
 #include "blob.hpp"
 #include "options.hpp"
 #include "endpoint.hpp"
+#include "msg.hpp"
 
 namespace zmq
 {
-class msg_t;
 class pipe_t;
 
 //  Create a pipepair for bi-directional transfer of messages.
@@ -147,6 +147,9 @@ class pipe_t ZMQ_FINAL : public object_t,
 
     void send_stats_to_peer (own_t *socket_base_);
 
+    void send_disconnect_msg ();
+    void set_disconnect_msg (const std::vector<unsigned char> &disconnect_);
+
   private:
     //  Type of the underlying lock-free pipe.
     typedef ypipe_base_t<msg_t> upipe_t;
@@ -257,6 +260,9 @@ class pipe_t ZMQ_FINAL : public object_t,
     // The endpoints of this pipe.
     endpoint_uri_pair_t _endpoint_pair;
 
+    // Disconnect msg
+    msg_t _disconnect_msg;
+
     ZMQ_NON_COPYABLE_NOR_MOVABLE (pipe_t)
 };