# Poco::Net

# class TCPServer

Library: Net
Package: TCPServer
Header: Poco/Net/TCPServer.h

## Description

This class implements a multithreaded TCP server.

The server uses a ServerSocket to listen for incoming connections. The ServerSocket must have been bound to an address before it is passed to the TCPServer constructor. Additionally, the ServerSocket must be put into listening state before the TCPServer is started by calling the start() method.

The server uses a thread pool to assign threads to incoming connections. Before incoming connections are assigned to a connection thread, they are put into a queue. Connection threads fetch new connections from the queue as soon as they become free. Thus, a connection thread may serve more than one connection.

As soon as a connection thread fetches the next connection from the queue, it creates a TCPServerConnection object for it (using the TCPServerConnectionFactory passed to the constructor) and calls the TCPServerConnection's start() method. When the start() method returns, the connection object is deleted.

The number of connection threads is adjusted dynamically, depending on the number of connections waiting to be served.

It is possible to specify a maximum number of queued connections. This prevents the connection queue from overflowing in the case of an extreme server load. In such a case, connections that cannot be queued are silently and immediately closed.

TCPServer uses a separate thread to accept incoming connections. Thus, the call to start() returns immediately, and the server continues to run in the background.

To stop the server from accepting new connections, call stop().

After calling stop(), no new connections will be accepted and all queued connections will be discarded. Already served connections, however, will continue being served.

## Inheritance

Direct Base Classes: Poco::Runnable

All Base Classes: Poco::Runnable

Known Derived Classes: HTTPServer

## Member Summary

Member Functions: currentConnections, currentThreads, getConnectionFilter, maxConcurrentConnections, maxThreads, params, port, queuedConnections, refusedConnections, run, setConnectionFilter, socket, start, stop, threadName, totalConnections

Inherited Functions: run

## Constructors

### TCPServer

TCPServer(
TCPServerConnectionFactory::Ptr pFactory,
Poco::UInt16 portNumber = 0,
TCPServerParams::Ptr pParams = nullptr
);

Creates the TCPServer, with ServerSocket listening on the given port. Default port is zero, allowing any available port. The port number can be queried through TCPServer::port() member.

The server takes ownership of the TCPServerConnectionFactory and deletes it when it's no longer needed.

The server also takes ownership of the TCPServerParams object. If no TCPServerParams object is given, the server's TCPServerDispatcher creates its own one.

New threads are taken from the default thread pool.

### TCPServer

TCPServer(
TCPServerConnectionFactory::Ptr pFactory,
const ServerSocket & socket,
TCPServerParams::Ptr pParams = nullptr
);

Creates the TCPServer, using the given ServerSocket.

The server takes ownership of the TCPServerConnectionFactory and deletes it when it's no longer needed.

The server also takes ownership of the TCPServerParams object. If no TCPServerParams object is given, the server's TCPServerDispatcher creates its own one.

New threads are taken from the default thread pool.

### TCPServer

TCPServer(
TCPServerConnectionFactory::Ptr pFactory,
Poco::ThreadPool & threadPool,
const ServerSocket & socket,
TCPServerParams::Ptr pParams = nullptr
);

Creates the TCPServer, using the given ServerSocket.

The server takes ownership of the TCPServerConnectionFactory and deletes it when it's no longer needed.

The server also takes ownership of the TCPServerParams object. If no TCPServerParams object is given, the server's TCPServerDispatcher creates its own one.

New threads are taken from the given thread pool.

## Destructor

### ~TCPServer

virtual ~TCPServer();

Destroys the TCPServer and its TCPServerConnectionFactory.

## Member Functions

### currentConnections

int currentConnections() const;

Returns the number of currently handled connections.

### currentThreads

int currentThreads() const;

Returns the number of currently used connection threads.

### getConnectionFilter

TCPServerConnectionFilter::Ptr getConnectionFilter() const;

Returns the TCPServerConnectionFilter set with setConnectionFilter(), or null pointer if no filter has been set.

### maxConcurrentConnections

int maxConcurrentConnections() const;

Returns the maximum number of concurrently handled connections.

### maxThreads

int maxThreads() const;

Returns the maximum number of threads available.

### params

const TCPServerParams & params() const;

Returns a const reference to the TCPServerParam object used by the server's TCPServerDispatcher.

### port

Poco::UInt16 port() const;

Returns the port the server socket listens on.

### queuedConnections

int queuedConnections() const;

Returns the number of queued connections.

### refusedConnections

int refusedConnections() const;

Returns the number of refused connections.

### setConnectionFilter

void setConnectionFilter(
const TCPServerConnectionFilter::Ptr & pFilter
);

Sets a TCPServerConnectionFilter. Can also be used to remove a filter by passing a null pointer.

To avoid a potential race condition, the filter must be set before the TCPServer is started. Trying to set the filter after start() has been called will trigger an assertion.

### socket

const ServerSocket & socket() const;

Returns the underlying server socket.

### start

void start();

Starts the server. A new thread will be created that waits for and accepts incoming connections.

Before start() is called, the ServerSocket passed to TCPServer must have been bound and put into listening state.

### stop

void stop();

Stops the server.

No new connections will be accepted. Already handled connections will continue to be served.

Once the server has been stopped, it cannot be restarted.

### totalConnections

Int64 totalConnections() const;

Returns the total number of handled connections.

### run

void run();

Runs the server. The server will run until the stop() method is called, or the server object is destroyed, which implicitly calls the stop() method.

See also: Poco::Runnable::run()

### threadName

static std::string threadName(
const ServerSocket & socket
);

Returns a thread name for the server thread.