diff --git a/build/src.pro b/build/src.pro
index e29d0c8..5dbd16f 100644
--- a/build/src.pro
+++ b/build/src.pro
@@ -17,10 +17,12 @@ HEADERS += \
     ../include/shm.h \
     ../include/circ_elem_array.h \
     ../include/circ_queue.h \
-    ../include/ipc.h
+    ../include/ipc.h \
+    ../include/def.h
 
 SOURCES += \
-    ../src/shm.cpp
+    ../src/shm.cpp \
+    ../src/ipc.cpp
 
 unix {
 
diff --git a/include/circ_elem_array.h b/include/circ_elem_array.h
index 3be3e9a..198a075 100644
--- a/include/circ_elem_array.h
+++ b/include/circ_elem_array.h
@@ -1,18 +1,14 @@
 #pragma once
 
-#include <cstddef>
-#include <cstdint>
 #include <cstring>
 #include <atomic>
 #include <utility>
-#include <limits>
 #include <algorithm>
 #include <thread>
 
+#include "def.h"
+
 namespace ipc {
-
-using byte_t = std::uint8_t;
-
 namespace circ {
 
 struct alignas(std::max_align_t) elem_array_head {
diff --git a/include/circ_queue.h b/include/circ_queue.h
index c5fc6e5..71ddddd 100644
--- a/include/circ_queue.h
+++ b/include/circ_queue.h
@@ -6,14 +6,10 @@
 #include <utility>
 #include <algorithm>
 
+#include "def.h"
 #include "circ_elem_array.h"
 
 namespace ipc {
-
-enum : std::size_t {
-    error_count = std::numeric_limits<std::size_t>::max()
-};
-
 namespace circ {
 
 template <typename T>
@@ -24,6 +20,7 @@ public:
 private:
     array_t* elems_ = nullptr;
     typename std::result_of<decltype(&array_t::cursor)(array_t)>::type cursor_ = 0;
+    bool connected_ = false;
 
 public:
     queue(void) = default;
@@ -52,19 +49,31 @@ public:
 
     std::size_t connect(void) {
         if (elems_ == nullptr) return error_count;
-        cursor_ = elems_->cursor();
+        if (connected_) return error_count;
+        connected_ = true;
         return elems_->connect();
     }
 
     std::size_t disconnect(void) {
         if (elems_ == nullptr) return error_count;
+        if (!connected_) return error_count;
+        connected_ = false;
         return elems_->disconnect();
     }
 
+    std::size_t conn_count(void) const {
+        return (elems_ == nullptr) ? error_count : elems_->conn_count();
+    }
+
+    bool connected(void) const {
+        return connected_;
+    }
+
     array_t* attach(array_t* arr) {
         if (arr == nullptr) return nullptr;
         auto old = elems_;
-        elems_ = arr;
+        elems_  = arr;
+        cursor_ = elems_->cursor();
         return old;
     }
 
@@ -75,16 +84,13 @@ public:
         return old;
     }
 
-    std::size_t conn_count(void) const {
-        return (elems_ == nullptr) ? error_count : elems_->conn_count();
-    }
-
     template <typename... P>
-    void push(P&&... params) {
-        if (elems_ == nullptr) return;
+    bool push(P&&... params) {
+        if (elems_ == nullptr) return false;
         auto ptr = elems_->acquire();
         ::new (ptr) T { std::forward<P>(params)... };
         elems_->commit(ptr);
+        return true;
     }
 
     T pop(void) {
diff --git a/include/def.h b/include/def.h
new file mode 100644
index 0000000..67b4785
--- /dev/null
+++ b/include/def.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+
+namespace ipc {
+
+// types
+
+using byte_t = std::uint8_t;
+
+// constants
+
+enum : std::size_t {
+    error_count = std::numeric_limits<std::size_t>::max(),
+    data_length = 16
+};
+
+} // namespace ipc
diff --git a/include/ipc.h b/include/ipc.h
index 68a795b..dd5a4e4 100644
--- a/include/ipc.h
+++ b/include/ipc.h
@@ -1,9 +1,19 @@
 #pragma once
 
+#include <vector>
+
 #include "export.h"
+#include "def.h"
+#include "shm.h"
 
 namespace ipc {
 
+using shm::handle_t;
 
+IPC_EXPORT handle_t connect   (std::string const & name);
+IPC_EXPORT void     disconnect(handle_t h);
+
+IPC_EXPORT bool                send(handle_t h, byte_t* data, int size);
+IPC_EXPORT std::vector<byte_t> recv(handle_t h);
 
 } // namespace ipc
diff --git a/src/ipc.cpp b/src/ipc.cpp
new file mode 100644
index 0000000..5b388bf
--- /dev/null
+++ b/src/ipc.cpp
@@ -0,0 +1,128 @@
+#include <unordered_map>
+#include <memory>
+#include <type_traits>
+#include <cstring>
+#include <algorithm>
+
+#include "ipc.h"
+#include "circ_queue.h"
+
+namespace {
+
+using namespace ipc;
+
+using data_t = byte_t[data_length];
+
+struct msg_t {
+    int    remain_;
+    data_t data_;
+};
+
+using queue_t = circ::queue<msg_t>;
+using guard_t = std::unique_ptr<std::remove_pointer_t<handle_t>, void(*)(handle_t)>;
+
+std::unordered_map<handle_t, queue_t> h2q__;
+
+queue_t* queue_of(handle_t h) {
+    if (h == nullptr) {
+        return nullptr;
+    }
+    auto it = h2q__.find(h);
+    if (it == h2q__.end()) {
+        return nullptr;
+    }
+    if (it->second.elems() == nullptr) {
+        return nullptr;
+    }
+    return &(it->second);
+}
+
+} // internal-linkage
+
+namespace ipc {
+
+handle_t connect(std::string const & name) {
+    auto h = shm::acquire(name, sizeof(queue_t));
+    if (h == nullptr) {
+        return nullptr;
+    }
+    guard_t h_guard {
+        h, [](handle_t h) { shm::release(h, sizeof(queue_t)); }
+    };
+    auto mem = shm::open(h);
+    if (mem == nullptr) {
+        return nullptr;
+    }
+    h2q__[h].attach(static_cast<queue_t::array_t*>(mem));
+    h_guard.release();
+    return h;
+}
+
+void disconnect(handle_t h) {
+    auto it = h2q__.find(h);
+    if (it == h2q__.end()) return;
+    it->second.disconnect();
+    shm::close(it->second.detach());
+    shm::release(h, sizeof(queue_t));
+    h2q__.erase(it);
+}
+
+bool send(handle_t h, byte_t* data, int size) {
+    if (data == nullptr) {
+        return false;
+    }
+    if (size <= 0) {
+        return false;
+    }
+    auto queue = queue_of(h);
+    if (queue == nullptr) {
+        return false;
+    }
+    queue_t drop_box { queue->elems() };
+    int offset = 0;
+    for (int i = 0; i < (size / static_cast<int>(data_length)); ++i, offset += data_length) {
+        msg_t msg {
+            size - offset - static_cast<int>(data_length),
+            { 0 }
+        };
+        std::memcpy(msg.data_, data + offset, data_length);
+        drop_box.push(msg);
+    }
+    int remain = size - offset;
+    if (remain > 0) {
+        msg_t msg { remain - static_cast<int>(data_length), { 0 } };
+        std::memcpy(msg.data_, data + offset, static_cast<std::size_t>(remain));
+        drop_box.push(msg);
+    }
+    return true;
+}
+
+std::vector<byte_t> recv(handle_t h) {
+    std::vector<byte_t> all;
+    auto queue = queue_of(h);
+    if (queue == nullptr) {
+        return all;
+    }
+    if (!queue->connected()) {
+        queue->connect();
+    }
+    do {
+        auto msg = queue->pop();
+        auto last_size = all.size();
+        if (msg.remain_ > 0) {
+            all.resize(last_size + data_length);
+            std::memcpy(all.data() + last_size, msg.data_, data_length);
+        }
+        else {
+            // remain_ is minus & abs(remain_) < data_length
+            std::size_t remain = static_cast<std::size_t>(
+                                 static_cast<int>(data_length) + msg.remain_);
+            all.resize(last_size + remain);
+            std::memcpy(all.data() + last_size, msg.data_, remain);
+            break;
+        }
+    } while(1);
+    return all;
+}
+
+} // namespace ipc
diff --git a/src/platform/shm_linux.cpp b/src/platform/shm_linux.cpp
index 414fab3..7d8897d 100644
--- a/src/platform/shm_linux.cpp
+++ b/src/platform/shm_linux.cpp
@@ -1,11 +1,11 @@
-#include "shm.h"
-
 #include <sys/shm.h>
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <unistd.h>
 #include <fcntl.h>
 
+#include "shm.h"
+
 namespace ipc {
 namespace shm {
 
diff --git a/src/platform/shm_win.cpp b/src/platform/shm_win.cpp
index c5082b2..7caa421 100644
--- a/src/platform/shm_win.cpp
+++ b/src/platform/shm_win.cpp
@@ -1,11 +1,11 @@
-#include "shm.h"
-
 #include <windows.h>
 
 #include <type_traits>
 #include <locale>
 #include <codecvt>
 
+#include "shm.h"
+
 namespace {
 
 template <typename T = TCHAR>
diff --git a/src/shm.cpp b/src/shm.cpp
index ac694dc..f60f6ea 100644
--- a/src/shm.cpp
+++ b/src/shm.cpp
@@ -1,7 +1,7 @@
-#include "shm.h"
-
 #include <utility>
 
+#include "shm.h"
+
 namespace ipc {
 namespace shm {