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Connections Manager

The connections manager is the actor in charge of providing:

  • A TCP server bound to the address indicated by the configuration file
  • As many TCP clients as requested, connected to the addresses requested by the Sessions Manager


The Connections Manager actor has no proper state.

/// Connections manager actor
pub struct ConnectionsManager;

Actor creation and registration

The creation of the connections manager actor and its registration into the system registry are performed directly by the main process:

let connections_manager_addr = ConnectionsManager::default().start();


Incoming messages: Others -> Connections Manager

These are the messages supported by the connections manager handlers:

Message Input type Output type Description
InboundTcpConnect TcpStream () Request to create a session from an incoming TCP connection
OutboundTcpConnect SocketAddr () Request to create a start a TCP connection to a peer

The way other actors will communicate with the connections manager is:

  1. Get the address of the connections manager from the registry:

    // Get connections manager address
    let connections_manager_addr = System::current().registry().get::<ConnectionsManager>();

  2. Use any of the sending methods provided by the address (do_send(), try_send(), send()) to send a message to the actor:

    // Send a message to the connections manager
    connections_manager_addr.do_send(OutboundTcpConnect { address });

InboundTcpConnect message

The InboundTcpConnect message is sent to the ConnectionsManager by the ConnectionsManager itself.

In the started method of the connections manager actor, the server address is requested from the ConfigManager actor and a TCP listener is created and bound to that address:

// Get address to launch the server
let server_address = "".parse().unwrap();

// Bind TCP listener to this address
let listener = TcpListener::bind(&server_address).unwrap();

For each incoming TCP connection that comes into the TCP listener, an InboundTcpConnect message is created from the TCP stream and sent to the actor:

// Add message stream which returns an InboundTcpConnect for each incoming TCP connection
        .map_err(|_| ())

When an InboundTcpConnect message arrives at the connections manager actor, the creation of a new Inbound session is requested to the SessionsManager:

/// Method to handle the InboundTcpConnect message
fn handle(&mut self, msg: InboundTcpConnect, _ctx: &mut Self::Context) {
    // Request the creation of a new session actor from connection
    ConnectionsManager::request_session_creation(, SessionType::Inbound);

OutboundTcpConnect message

The OutboundTcpConnect message is sent to the ConnectionsManager by the SessionsManager.

When an OutboundTcpConnect message arrives at the connections manager actor, several actions are performed:

  • Send a ConnectAddr message to the Resolver actor to connect to the requested peer address
  • Handle the result:
    • If an error is returned, do nothing but log it
    • If successful, request the creation of an Outbound session to the SessionsManager
/// Method to handle the OutboundTcpConnect message
fn handle(&mut self, msg: OutboundTcpConnect, ctx: &mut Self::Context) {
    // Get resolver from registry and send a ConnectAddr message to it
        .then(|res, _act, _ctx| ConnectionsManager::process_connect_addr_response(res))

Outgoing messages: Connections Manager -> Others

These are the messages sent by the connections manager:

Message Destination Input type Output type Description
GetConfig ConfigManager () Result<Config, io::Error> Request the configuration
ConnectAddr Resolver SocketAddr Result<TcpStream, ResolverError> Request a TCP conn to an address
Create SessionsManager TcpStream, SessionType () Request the creation of a session


This message is sent to the ConfigManager actor when the connections manager actor is started.

The return value is used to get the TCP server address of the Witnet node and launch it.

For further information, see ConfigManager.


This message is sent to the Resolver actor when an OutboundTcpConnect message is received.

Upon reception of this message, the Resolver tries to open a TCP connection to the address specified in the message.

For further information, see Resolver.


This message is sent to the SessionsManager actor when a TCP connection is established to request the creation of a session.

For further information, see SessionsManager.

Further information

The full source code of the ConnectionsManager can be found at