diff --git a/README.md b/README.md
index f14a695..e5e3940 100644
--- a/README.md
+++ b/README.md
@@ -109,6 +109,15 @@
 - [I/O Multiplex (I/O多路复用) (Client)](https://leven-cn.github.io/python-cookbook/cookbook/core/net/io_multiplex_client)
 - [Pack/Unpack Binary Data - `struct`](https://leven-cn.github.io/python-cookbook/cookbook/core/net/struct)
 
+### Asynchronous I/O (异步 I/O)
+
+- [Coroutine (协程)](https://leven-cn.github.io/python-cookbook/cookbook/core/asyncio/coroutine)
+- [Run coroutines concurrently (并发执行协程)](https://leven-cn.github.io/python-cookbook/cookbook/core/asyncio/coroutine_concurrent)
+- [Scheduled Tasks (调度任务)](https://leven-cn.github.io/python-cookbook/cookbook/core/asyncio/schedule)
+- [Wait](https://leven-cn.github.io/python-cookbook/cookbook/core/asyncio/wait)
+- [TCP Server](https://leven-cn.github.io/python-cookbook/cookbook/core/asyncio/tcp_server)
+- [TCP Client](https://leven-cn.github.io/python-cookbook/cookbook/core/asyncio/tcp_client)
+
 ## Build (构建)
 
 ### Command-Line Arguments Parser
@@ -207,20 +216,13 @@
   - [IPC - Socket Pair](https://leven-cn.github.io/python-cookbook/recipes/core/ipc_socketpair)
   - [IPC - UNIX Domain Socket (UDS, UNIX 域套接字) Server and Client](https://leven-cn.github.io/python-cookbook/recipes/core/ipc_unix_domain_socket)
 - Asynchronous I/O (异步 I/O)
-  - [Coroutine (协程)](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_coroutine)
-  - [Chain coroutines (串链协程)](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_coroutine_chain)
-  - [Run coroutines Concurrently (并发执行协程)](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_coroutine_chain)
-  - [Scheduled Tasks (调度任务)](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_schedule)
-  - [Wait](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_wait)
   - [Nonblocking Main Thread](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_nonblocking)
   - [Synchronization Primitives: Lock](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_synchronization_lock)
   - [Synchronization Primitives: Event](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_synchronization_event)
   - [Synchronization Primitives: Condition](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_synchronization_condition)
   - [Synchronization Primitives: Semapore (信号量)](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_synchronization_semapore)
   - [Queue (队列)](https://leven-cn.github.io/python-cookbook/recipes/core/asyncio_queue)
-  - [TCP Server (High-Level APIs)](https://leven-cn.github.io/python-cookbook/recipes/core/tcp_server_asyncio_high_api)
   - [TCP Server (Low-Level APIs)](https://leven-cn.github.io/python-cookbook/recipes/core/tcp_server_asyncio_low_api)
-  - [TCP Client - (High-Level APIs)](https://leven-cn.github.io/python-cookbook/recipes/core/tcp_client_asyncio_high_api)
   - [TCP Client - (Low-Level APIs)](https://leven-cn.github.io/python-cookbook/recipes/core/tcp_client_asyncio_low_api)
   - [UDP Server](https://leven-cn.github.io/python-cookbook/recipes/core/udp_server_asyncio)
   - [UDP Client](https://leven-cn.github.io/python-cookbook/recipes/core/udp_client_asyncio)
diff --git a/recipes/core/asyncio_coroutine.md b/cookbook/core/asyncio/coroutine.md
similarity index 60%
rename from recipes/core/asyncio_coroutine.md
rename to cookbook/core/asyncio/coroutine.md
index 3019703..566c11e 100644
--- a/recipes/core/asyncio_coroutine.md
+++ b/cookbook/core/asyncio/coroutine.md
@@ -1,11 +1,8 @@
-# Asynchronous I/O - Create coroutine
+# Asynchronous I/O - Coroutine
 
-## Solution
+## Recipes
 
 ```python
-"""Asynchronous I/O - coroutine.
-"""
-
 import asyncio
 import logging
 import sys
@@ -15,9 +12,21 @@ logging.basicConfig(
 )
 
 
-async def coroutine(arg: int):
+async def coroutine(arg: int) -> tuple[int, str, str]:
+    """Coroutine demo."""
     logging.debug(f'run coroutine: {arg}')
-    return arg + 1
+
+    result_1: str = await task(1, 1.0)
+    result_2: str = await task(2, 1.5)
+
+    return arg + 1, result_1, result_2
+
+
+async def task(num: int, wait: float) -> str:
+    """Coroutine task demo."""
+    logging.debug(f'run task {num}, wait {wait} seconds')
+    await asyncio.sleep(wait)
+    return f'task {num} result'
 
 
 coro = coroutine(1)
@@ -26,7 +35,9 @@ if sys.version_info >= (3, 7):  # Python 3.7+
     logging.debug(f'result: {result}')
 else:
     # Low-level APIs
-    loop = asyncio.get_event_loop()
+    # `get_running_loop()` has been added since Python 3.7.
+    # `get_event_loop()` has been deprecated since Python 3.10.
+    loop = asyncio.get_running_loop()
     try:
         logging.debug('starting event loop')
         result = loop.run_until_complete(coro)
@@ -35,8 +46,6 @@ else:
         loop.close()
 ```
 
-See [source code](https://github.com/leven-cn/python-cookbook/blob/main/examples/core/asyncio_coroutine.py)
-
 ## References
 
 - [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
diff --git a/recipes/core/asyncio_coroutine_concurrent.md b/cookbook/core/asyncio/coroutine_concurrent.md
similarity index 92%
rename from recipes/core/asyncio_coroutine_concurrent.md
rename to cookbook/core/asyncio/coroutine_concurrent.md
index 85f4410..e730c83 100644
--- a/recipes/core/asyncio_coroutine_concurrent.md
+++ b/cookbook/core/asyncio/coroutine_concurrent.md
@@ -1,11 +1,8 @@
 # Asynchronous I/O - Run coroutines Concurrently
 
-## Solution
+## Recipes
 
 ```python
-"""Asynchronous I/O - Run coroutines concurrently.
-"""
-
 import asyncio
 import logging
 
@@ -97,8 +94,6 @@ result = asyncio.run(main())  # Python 3.7+
 logging.debug(f'result: {result}')
 ```
 
-See [source code](https://github.com/leven-cn/python-cookbook/blob/main/examples/core/asyncio_coroutine_concurrent.py)
-
 ## References
 
 - [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
diff --git a/recipes/core/asyncio_schedule.md b/cookbook/core/asyncio/schedule.md
similarity index 92%
rename from recipes/core/asyncio_schedule.md
rename to cookbook/core/asyncio/schedule.md
index 58f169d..8479bf7 100644
--- a/recipes/core/asyncio_schedule.md
+++ b/cookbook/core/asyncio/schedule.md
@@ -1,11 +1,8 @@
 # Asynchronous I/O - Scheduled Tasks
 
-## Solution
+## Recipes
 
 ```python
-"""Asynchronous I/O - Scheduled Tasks.
-"""
-
 import asyncio
 import logging
 import time
@@ -70,8 +67,6 @@ result = asyncio.run(main())
 logging.debug(f'result: {result}')
 ```
 
-See [source code](https://github.com/leven-cn/python-cookbook/blob/main/examples/core/asyncio_schedule.py)
-
 ## References
 
 - [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
diff --git a/recipes/core/tcp_client_asyncio_high_api.md b/cookbook/core/asyncio/tcp_client.md
similarity index 80%
rename from recipes/core/tcp_client_asyncio_high_api.md
rename to cookbook/core/asyncio/tcp_client.md
index c07a081..e74d7a8 100644
--- a/recipes/core/tcp_client_asyncio_high_api.md
+++ b/cookbook/core/asyncio/tcp_client.md
@@ -1,11 +1,8 @@
-# TCP Client - Asynchronous I/O (High-Level APIs)
+# TCP Client - Asynchronous I/O
 
 ## Solution
 
 ```python
-"""TCP Client - Asynchronous I/O (High-Level APIs).
-"""
-
 import asyncio
 import logging
 
@@ -32,8 +29,6 @@ async def tcp_echo_client(data: bytes):
 asyncio.run(tcp_echo_client(b'Hello World!'))  # Python 3.7+
 ```
 
-See [source code](https://github.com/leven-cn/python-cookbook/blob/main/examples/core/tcp_client_asyncio_high_api.py)
-
 ## References
 
 - [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
diff --git a/cookbook/core/asyncio/tcp_server.md b/cookbook/core/asyncio/tcp_server.md
new file mode 100644
index 0000000..8190c1f
--- /dev/null
+++ b/cookbook/core/asyncio/tcp_server.md
@@ -0,0 +1,134 @@
+# TCP Server - Asynchronous I/O
+
+## Recipes
+
+```python
+import asyncio
+import logging
+import socket
+import sys
+
+logging.basicConfig(
+    level=logging.DEBUG, style='{', format='[{threadName} ({thread})] {message}'
+)
+
+recv_bufsize: int | None = None
+send_bufsize: int | None = None
+
+
+async def handle_echo(
+    reader: asyncio.StreamReader, writer: asyncio.StreamWriter
+) -> None:
+    client_address = writer.get_extra_info('peername')
+    logging.debug(f'connected from {client_address}')
+
+    sock: socket.socket = writer.get_extra_info('socket')
+    assert sock.type is socket.SOCK_STREAM
+    assert sock.getpeername() == client_address
+    assert sock.getsockname() == writer.get_extra_info('sockname')  # server address
+    assert sock.gettimeout() == 0
+    assert bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY))
+    assert bool(sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR))
+    assert bool(sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT))
+    if hasattr(socket, 'TCP_QUICKACK'):
+        assert sys.platform == 'linux'
+        assert bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK))
+    assert bool(sock.getsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE))
+    if sys.platform == 'linux':  # Linux 2.4+
+        assert sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE) == 1800
+    elif hasattr(socket, 'TCP_KEEPALIVE'):  # macOS and Python 3.10+
+        assert sys.platform == 'darwin' and sys.version_info >= (3, 10)
+        assert not sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPALIVE) == 1800
+        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPALIVE, 1800)
+    assert sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT) == 5
+    assert sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL) == 15
+
+    # logging.debug(dir(sock))
+
+    # Recv
+    data = await reader.read(100)
+    logging.debug(f'recv: {data!r}')
+
+    # Send
+    writer.write(data)
+    await writer.drain()
+    logging.debug(f'sent: {data!r}')
+
+    writer.close()
+
+
+async def tcp_echo_server(
+    host: str,
+    port: int,
+    *,
+    accept_queue_size: int = socket.SOMAXCONN,
+    keep_alive_idle: int | None = None,
+    keep_alive_cnt: int | None = None,
+    keep_alive_intvl: int | None = None,
+    start_serving: bool = False,
+) -> None:
+    # Low-level APIs: loop.create_server()
+    server = await asyncio.start_server(
+        handle_echo,
+        host,
+        port,
+        reuse_address=True,
+        reuse_port=True,
+        backlog=accept_queue_size,
+        start_serving=start_serving,
+    )
+
+    # Prior to Python 3.7 `asyncio.Server.sockets` used to return an internal list of
+    # server sockets directly.
+    # In 3.7 a copy of that list is returned.
+    server_addressess = ', '.join(str(sock.getsockname()) for sock in server.sockets)
+    logging.debug(f'Serving on {server_addressess}')
+
+    for sock in server.sockets:
+        # Issue: ? The socket option `TCP_NODELAY` is set by default in Python 3.6+
+        assert not bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY))
+        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
+
+        # Keep-Alive
+        if (
+            keep_alive_cnt is not None
+            and keep_alive_intvl is not None
+            and keep_alive_idle is not None
+        ):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+            if sys.platform == 'linux':  # Linux 2.4+
+                sock.setsockopt(
+                    socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, keep_alive_idle
+                )
+            elif hasattr(socket, 'TCP_KEEPALIVE'):
+                assert sys.platform == 'darwin' and sys.version_info >= (3, 10)
+                sock.setsockopt(
+                    socket.IPPROTO_TCP, socket.TCP_KEEPALIVE, keep_alive_idle
+                )
+            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, keep_alive_cnt)
+            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, keep_alive_intvl)
+
+        # QUICK ACK
+        if hasattr(socket, 'TCP_QUICKACK'):
+            assert sys.platform == 'linux'
+            assert bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK))
+
+    # `asyncio.Server` object is an asynchronous context manager since Python 3.7.
+    if not start_serving:
+        async with server:
+            await server.serve_forever()
+
+
+asyncio.run(
+    tcp_echo_server(
+        '127.0.0.1', 8888, keep_alive_idle=1800, keep_alive_cnt=5, keep_alive_intvl=15
+    )
+)  # Python 3.7+
+```
+
+## References
+
+- [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
+- [Python - `socket` module](https://docs.python.org/3/library/socket.html)
+- [PEP 3156 – Asynchronous IO Support Rebooted: the "asyncio" Module](https://peps.python.org/pep-3156/)
+- [PEP 3151 – Reworking the OS and IO exception hierarchy](https://peps.python.org/pep-3151/)
diff --git a/recipes/core/asyncio_wait.md b/cookbook/core/asyncio/wait.md
similarity index 90%
rename from recipes/core/asyncio_wait.md
rename to cookbook/core/asyncio/wait.md
index 8359cb2..2b4fba6 100644
--- a/recipes/core/asyncio_wait.md
+++ b/cookbook/core/asyncio/wait.md
@@ -1,11 +1,8 @@
 # Asynchronous I/O - Wait
 
-## Solution
+## Recipes
 
 ```python
-"""Asynchronous I/O - Wait.
-"""
-
 import asyncio
 import logging
 
@@ -50,8 +47,6 @@ async def main():
 asyncio.run(main())  # Python 3.7+
 ```
 
-See [source code](https://github.com/leven-cn/python-cookbook/blob/main/examples/core/asyncio_wait.py)
-
 ## References
 
 - [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
diff --git a/examples/core/asyncio_coroutine.py b/examples/core/asyncio_coroutine.py
index 9a30bda..e800565 100644
--- a/examples/core/asyncio_coroutine.py
+++ b/examples/core/asyncio_coroutine.py
@@ -10,10 +10,21 @@
 )
 
 
-async def coroutine(arg: int) -> int:
+async def coroutine(arg: int) -> tuple[int, str, str]:
     """Coroutine demo."""
     logging.debug(f'run coroutine: {arg}')
-    return arg + 1
+
+    result_1: str = await task(1, 1.0)
+    result_2: str = await task(2, 1.5)
+
+    return arg + 1, result_1, result_2
+
+
+async def task(num: int, wait: float) -> str:
+    """Coroutine task demo."""
+    logging.debug(f'run task {num}, wait {wait} seconds')
+    await asyncio.sleep(wait)
+    return f'task {num} result'
 
 
 coro = coroutine(1)
diff --git a/examples/core/asyncio_coroutine_chain.py b/examples/core/asyncio_coroutine_chain.py
deleted file mode 100644
index 7c6a675..0000000
--- a/examples/core/asyncio_coroutine_chain.py
+++ /dev/null
@@ -1,31 +0,0 @@
-"""Asynchronous I/O - Chain coroutines.
-"""
-
-import asyncio
-import logging
-
-logging.basicConfig(
-    level=logging.DEBUG, style='{', format='[{threadName} ({thread})] {message}'
-)
-
-
-async def coroutine(arg: int) -> tuple[str, str]:
-    """Coroutine demo."""
-    logging.debug(f'run coroutine: {arg}')
-
-    result_1: str = await task(1, 1.0)
-    result_2: str = await task(2, 1.5)
-
-    return (result_1, result_2)
-
-
-async def task(num: int, wait: float) -> str:
-    """Coroutine task demo."""
-    logging.debug(f'run task {num}, wait {wait} seconds')
-    await asyncio.sleep(wait)
-    return f'task {num} result'
-
-
-coro = coroutine(1)
-result: tuple[str, str] = asyncio.run(coro)  # Python 3.7+
-logging.debug(f'result: {result}')
diff --git a/examples/core/tcp_client_asyncio_high_api.py b/examples/core/asyncio_tcp_client.py
similarity index 100%
rename from examples/core/tcp_client_asyncio_high_api.py
rename to examples/core/asyncio_tcp_client.py
diff --git a/examples/core/asyncio_tcp_server.py b/examples/core/asyncio_tcp_server.py
new file mode 100644
index 0000000..030dd41
--- /dev/null
+++ b/examples/core/asyncio_tcp_server.py
@@ -0,0 +1,124 @@
+"""TCP Server - Asynchronous I/O (High-Level APIs).
+"""
+
+import asyncio
+import logging
+import socket
+import sys
+
+logging.basicConfig(
+    level=logging.DEBUG, style='{', format='[{threadName} ({thread})] {message}'
+)
+
+recv_bufsize: int | None = None
+send_bufsize: int | None = None
+
+
+async def handle_echo(
+    reader: asyncio.StreamReader, writer: asyncio.StreamWriter
+) -> None:
+    client_address = writer.get_extra_info('peername')
+    logging.debug(f'connected from {client_address}')
+
+    sock: socket.socket = writer.get_extra_info('socket')
+    assert sock.type is socket.SOCK_STREAM
+    assert sock.getpeername() == client_address
+    assert sock.getsockname() == writer.get_extra_info('sockname')  # server address
+    assert sock.gettimeout() == 0
+    assert bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY))
+    assert bool(sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR))
+    assert bool(sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT))
+    if hasattr(socket, 'TCP_QUICKACK'):
+        assert sys.platform == 'linux'
+        assert bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK))
+    assert bool(sock.getsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE))
+    if sys.platform == 'linux':  # Linux 2.4+
+        assert sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE) == 1800
+    elif hasattr(socket, 'TCP_KEEPALIVE'):  # macOS and Python 3.10+
+        assert sys.platform == 'darwin' and sys.version_info >= (3, 10)
+        assert not sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPALIVE) == 1800
+        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPALIVE, 1800)
+    assert sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT) == 5
+    assert sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL) == 15
+
+    # logging.debug(dir(sock))
+
+    # Recv
+    data = await reader.read(100)
+    logging.debug(f'recv: {data!r}')
+
+    # Send
+    writer.write(data)
+    await writer.drain()
+    logging.debug(f'sent: {data!r}')
+
+    writer.close()
+
+
+async def tcp_echo_server(
+    host: str,
+    port: int,
+    *,
+    accept_queue_size: int = socket.SOMAXCONN,
+    keep_alive_idle: int | None = None,
+    keep_alive_cnt: int | None = None,
+    keep_alive_intvl: int | None = None,
+    start_serving: bool = False,
+) -> None:
+    # Low-level APIs: loop.create_server()
+    server = await asyncio.start_server(
+        handle_echo,
+        host,
+        port,
+        reuse_address=True,
+        reuse_port=True,
+        backlog=accept_queue_size,
+        start_serving=start_serving,
+    )
+
+    # Prior to Python 3.7 `asyncio.Server.sockets` used to return an internal list of
+    # server sockets directly.
+    # In 3.7 a copy of that list is returned.
+    server_addressess = ', '.join(str(sock.getsockname()) for sock in server.sockets)
+    logging.debug(f'Serving on {server_addressess}')
+
+    for sock in server.sockets:
+        # Issue: ? The socket option `TCP_NODELAY` is set by default in Python 3.6+
+        assert not bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY))
+        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
+
+        # Keep-Alive
+        if (
+            keep_alive_cnt is not None
+            and keep_alive_intvl is not None
+            and keep_alive_idle is not None
+        ):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+            if sys.platform == 'linux':  # Linux 2.4+
+                sock.setsockopt(
+                    socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, keep_alive_idle
+                )
+            elif hasattr(socket, 'TCP_KEEPALIVE'):
+                assert sys.platform == 'darwin' and sys.version_info >= (3, 10)
+                sock.setsockopt(
+                    socket.IPPROTO_TCP, socket.TCP_KEEPALIVE, keep_alive_idle
+                )
+            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, keep_alive_cnt)
+            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, keep_alive_intvl)
+
+        # QUICK ACK
+        if hasattr(socket, 'TCP_QUICKACK'):
+            assert sys.platform == 'linux'
+            assert bool(sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK))
+
+    # `asyncio.Server` object is an asynchronous context manager since Python 3.7.
+    if not start_serving:
+        async with server:
+            await server.serve_forever()
+
+
+asyncio.run(
+    tcp_echo_server(
+        '127.0.0.1', 8888, keep_alive_idle=1800, keep_alive_cnt=5, keep_alive_intvl=15
+    )
+)  # Python 3.7+
diff --git a/examples/core/tcp_server_asyncio_high_api.py b/examples/core/tcp_server_asyncio_high_api.py
deleted file mode 100644
index a599d96..0000000
--- a/examples/core/tcp_server_asyncio_high_api.py
+++ /dev/null
@@ -1,97 +0,0 @@
-"""TCP Server - Asynchronous I/O (High-Level APIs).
-"""
-
-from __future__ import annotations
-
-import asyncio
-import logging
-import socket
-import sys
-
-logging.basicConfig(
-    level=logging.DEBUG, style='{', format='[{threadName} ({thread})] {message}'
-)
-
-tcp_quickack = True
-recv_bufsize: int | None = None
-send_bufsize: int | None = None
-
-
-async def handle_echo(
-    reader: asyncio.StreamReader, writer: asyncio.StreamWriter
-) -> None:
-    # `socket.getpeername()`
-    client_address = writer.get_extra_info('peername')
-    logging.debug(f'connected from {client_address}')
-
-    # `socket.getsockname()`
-    # server_address = writer.get_extra_info('sockname')
-
-    sock = writer.get_extra_info('socket')
-    assert sock.type is socket.SOCK_STREAM
-    assert sock.getpeername() == client_address
-    assert sock.getsockname() == writer.get_extra_info('sockname')
-    assert sock.gettimeout() == 0.0
-    assert sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1
-    assert sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1
-
-    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
-
-    # TCP Keep-Alive
-    sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
-    if sys.platform == 'linux':  # Linux 2.4+
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, 1800)
-    elif sys.platform == 'darwin' and sys.version_info >= (3, 10):
-        sock.setsockopt(
-            socket.IPPROTO_TCP,
-            socket.TCP_KEEPALIVE,  # pylint: disable=no-member
-            1800,
-        )
-    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, 5)
-    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, 15)
-
-    # handle_tcp_quickack(sock, tcp_quickack)
-    # logging.debug(dir(sock))
-
-    # Recv
-    data = await reader.read(100)
-    logging.debug(f'recv: {data!r}')
-
-    # Send
-    writer.write(data)
-    await writer.drain()
-    logging.debug(f'sent: {data!r}')
-
-    writer.close()
-
-
-async def tcp_echo_server(
-    host: str,
-    port: int,
-    *,
-    backlog: int = socket.SOMAXCONN,
-) -> None:
-    # Low-level APIs: loop.create_server()
-    # The socket option `TCP_NODELAY` is set by default in Python 3.6+
-    server = await asyncio.start_server(
-        handle_echo,
-        host,
-        port,
-        reuse_address=True,
-        reuse_port=True,
-        backlog=backlog,
-        start_serving=True,
-    )
-
-    # Prior to Python 3.7 `asyncio.Server.sockets` used to return an internal list of
-    # server sockets directly.
-    # In 3.7 a copy of that list is returned.
-    server_addressess = ', '.join(str(sock.getsockname()) for sock in server.sockets)
-    logging.debug(f'Serving on {server_addressess}')
-
-    # `asyncio.Server` object is an asynchronous context manager since Python 3.7.
-    async with server:
-        await server.serve_forever()
-
-
-asyncio.run(tcp_echo_server('127.0.0.1', 8888))  # Python 3.7+
diff --git a/recipes/core/asyncio_coroutine_chain.md b/recipes/core/asyncio_coroutine_chain.md
deleted file mode 100644
index 576e349..0000000
--- a/recipes/core/asyncio_coroutine_chain.md
+++ /dev/null
@@ -1,42 +0,0 @@
-# Asynchronous I/O - Create Chain coroutines
-
-## Solution
-
-```python
-"""Asynchronous I/O - Chain coroutines.
-"""
-
-import asyncio
-import logging
-
-logging.basicConfig(
-    level=logging.DEBUG, style='{', format='[{threadName} ({thread})] {message}'
-)
-
-
-async def coroutine(arg: int):
-    logging.debug(f'run coroutine: {arg}')
-
-    result_1 = await task(1, 1.0)
-    result_2 = await task(2, 1.5)
-
-    return (result_1, result_2)
-
-
-async def task(num: int, wait: float):
-    logging.debug(f'run task {num}, wait {wait} seconds')
-    await asyncio.sleep(wait)
-    return f'task {num} result'
-
-
-coro = coroutine(1)
-result = asyncio.run(coro)  # Python 3.7+
-logging.debug(f'result: {result}')
-```
-
-See [source code](https://github.com/leven-cn/python-cookbook/blob/main/examples/core/asyncio_coroutine_chain.py)
-
-## References
-
-- [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
-- [PEP 3156 – Asynchronous IO Support Rebooted: the "asyncio" Module](https://peps.python.org/pep-3156/)
diff --git a/recipes/core/tcp_server_asyncio_high_api.md b/recipes/core/tcp_server_asyncio_high_api.md
deleted file mode 100644
index c6a185a..0000000
--- a/recipes/core/tcp_server_asyncio_high_api.md
+++ /dev/null
@@ -1,109 +0,0 @@
-# TCP Server - Asynchronous I/O (High-Level APIs)
-
-## Solution
-
-```python
-"""TCP Server - Asynchronous I/O (High-Level APIs).
-"""
-
-# PEP 604, Allow writing union types as X | Y (Python 3.10+)
-from __future__ import annotations
-
-import asyncio
-import logging
-import socket
-
-from net import (
-    handle_socket_bufsize,
-    handle_tcp_quickack,
-)
-
-logging.basicConfig(
-    level=logging.DEBUG, style='{', format='[{threadName} ({thread})] {message}'
-)
-
-tcp_quickack = True
-recv_bufsize: int | None = None
-send_bufsize: int | None = None
-
-
-async def handle_echo(reader: asyncio.StreamReader, writer: asyncio.StreamWriter):
-    # `socket.getpeername()`
-    client_address = writer.get_extra_info('peername')
-    logging.debug(f'connected from {client_address}')
-
-    # `socket.getsockname()`
-    # server_address = writer.get_extra_info('sockname')
-
-    sock = writer.get_extra_info('socket')
-    assert sock.type is socket.SOCK_STREAM
-    assert sock.getpeername() == client_address
-    assert sock.getsockname() == writer.get_extra_info('sockname')
-    assert sock.gettimeout() == 0.0
-    assert sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1
-    assert sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1
-    handle_tcp_quickack(sock, tcp_quickack)
-    handle_socket_bufsize(sock, recv_bufsize, send_bufsize)
-    # logging.debug(dir(sock))
-
-    # Recv
-    data = await reader.read(100)
-    logging.debug(f'recv: {data!r}')
-
-    # Send
-    writer.write(data)
-    await writer.drain()
-    logging.debug(f'sent: {data!r}')
-
-    writer.close()
-
-
-async def tcp_echo_server(
-    host: str,
-    port: int,
-    *,
-    backlog: int = 100,
-):
-    # Low-level APIs: loop.create_server()
-    # The socket option `TCP_NODELAY` is set by default in Python 3.6+
-    server = await asyncio.start_server(
-        handle_echo,
-        host,
-        port,
-        reuse_address=True,
-        reuse_port=True,
-        backlog=backlog,
-        start_serving=True,
-    )
-
-    # Prior to Python 3.7 `asyncio.Server.sockets` used to return an internal list of
-    # server sockets directly.
-    # In 3.7 a copy of that list is returned.
-    server_addressess = ', '.join(str(sock.getsockname()) for sock in server.sockets)
-    logging.debug(f'Serving on {server_addressess}')
-
-    # `asyncio.Server` object is an asynchronous context manager since Python 3.7.
-    async with server:
-        await server.serve_forever()
-
-
-asyncio.run(tcp_echo_server('127.0.0.1', 8888))  # Python 3.7+
-```
-
-## More
-
-- [TCP Reuse Address](tcp_reuse_address)
-- [Reuse Port](reuse_port)
-- [TCP/UDP (Recv/Send) Buffer Size](net_buffer_size)
-- [TCP `listen()` Queue](tcp_listen_queue)
-- [TCP Keep-Alive](tcp_keepalive)
-- [TCP Nodelay (Dsiable Nagle's Algorithm)](tcp_nodelay)
-- [TCP Quick ACK (Disable Delayed ACK (延迟确认))](tcp_quickack)
-- [TCP Slow Start (慢启动)](../../more/core/tcp_slowstart)
-
-## References
-
-- [Python - `asyncio` module](https://docs.python.org/3/library/asyncio.html)
-- [Python - `socket` module](https://docs.python.org/3/library/socket.html)
-- [PEP 3156 – Asynchronous IO Support Rebooted: the "asyncio" Module](https://peps.python.org/pep-3156/)
-- [PEP 3151 – Reworking the OS and IO exception hierarchy](https://peps.python.org/pep-3151/)