diff --git a/demo/chat/main.cpp b/demo/chat/main.cpp
index 8065181..eb71573 100644
--- a/demo/chat/main.cpp
+++ b/demo/chat/main.cpp
@@ -1,37 +1,56 @@
 #include <iostream>
 #include <string>
 #include <thread>
+#include <regex>
 
 #include "ipc.h"
 
+namespace ipc {
+namespace detail {
+
+IPC_EXPORT std::size_t calc_unique_id();
+
+} // namespace detail
+} // namespace ipc
+
 namespace {
 
 char name__[] = "ipc-chat";
 char quit__[] = "q";
+char id__  [] = "c";
 
 } // namespace
 
 int main() {
-    std::string buf;
+    std::string buf, id = id__ + std::to_string(ipc::detail::calc_unique_id());
+    std::regex  reg { "(c\\d+)> (.*)" };
+
     ipc::channel cc { name__ };
 
-    std::thread r {[] {
+    std::thread r {[&id, &reg] {
         ipc::channel cc { name__ };
+        std::cout << id << " is ready." << std::endl;
         while (1) {
             auto buf = cc.recv();
             if (buf.empty()) continue;
             std::string dat { static_cast<char const *>(buf.data()), buf.size() - 1 };
-            if (dat == quit__) {
-                std::cout << "receiver quit..." << std::endl;
-                return;
+            std::smatch mid;
+            if (std::regex_match(dat, mid, reg)) {
+                if (mid.str(1) == id) {
+                    if (mid.str(2) == quit__) {
+                        std::cout << "receiver quit..." << std::endl;
+                        return;
+                    }
+                    continue;
+                }
             }
-            std::cout << "> " << dat << std::endl;
+            std::cout << dat << std::endl;
         }
     }};
 
     while (1) {
         std::cin >> buf;
-        cc.send(buf);
+        cc.send(id + "> " + buf);
         if (buf == quit__) break;
     }
 
diff --git a/src/platform/waiter_win.h b/src/platform/waiter_win.h
index 3a09a9a..978dd3d 100644
--- a/src/platform/waiter_win.h
+++ b/src/platform/waiter_win.h
@@ -37,7 +37,6 @@ public:
     }
 
     bool post(long count = 1) {
-        if (count <= 0) return true;
         return !!::ReleaseSemaphore(h_, count, NULL);
     }
 };
@@ -116,10 +115,12 @@ public:
     void broadcast(handle_t& h) {
         if (h == invalid()) return;
         IPC_UNUSED_ auto guard = ipc::detail::unique_lock(mtx(h));
-        sem(h).post(counter_);
-        while (counter_ > 0) {
-            -- counter_;
-            han(h).wait();
+        if (counter_ > 0) {
+            sem(h).post(counter_);
+            do {
+                -- counter_;
+                han(h).wait();
+            } while (counter_ > 0);
         }
     }
 };