# Python SocketServer Module

The `socketserver` module simplifies the task of writing network servers. It provides classes for handling TCP, UDP, and Unix domain sockets.

## Importing the Module

```python
import socketserver
```

## Creating a Request Handler

To create a request handler, you must subclass `socketserver.BaseRequestHandler` and override the `handle()` method.

```python
class MyTCPHandler(socketserver.BaseRequestHandler):
    def handle(self):
        # self.request is the TCP socket connected to the client
        self.data = self.request.recv(1024).strip()
        print("{} wrote:".format(self.client_address[0]))
        print(self.data)
        # just send back the same data, but upper-cased
        self.request.sendall(self.data.upper())
```

## Creating a Server

You can create a server by instantiating one of the server classes, passing the server address and the request handler class.

### TCP Server

```python
HOST, PORT = "localhost", 9999

# Create the server, binding to localhost on port 9999
with socketserver.TCPServer((HOST, PORT), MyTCPHandler) as server:
    # Activate the server; this will keep running until you
    # interrupt the program with Ctrl-C
    server.serve_forever()
```

### UDP Server

For UDP, use `socketserver.UDPServer` and `socketserver.DatagramRequestHandler` (optional but recommended for convenience).

```python
class MyUDPHandler(socketserver.BaseRequestHandler):
    def handle(self):
        data = self.request[0].strip()
        socket = self.request[1]
        print("{} wrote:".format(self.client_address[0]))
        print(data)
        socket.sendto(data.upper(), self.client_address)

HOST, PORT = "localhost", 9999
with socketserver.UDPServer((HOST, PORT), MyUDPHandler) as server:
    server.serve_forever()
```

## Threading and Forking

To make the server asynchronous (handle multiple requests simultaneously), you can use the `ThreadingMixIn` or `ForkingMixIn` classes.

```python
class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer):
    pass
```

[[programming/python/python]]