NSBAppClient (C++)

Application-side client. Inherits from NSBClient.

Constructor

nsb::NSBAppClient nsb_conn(identifier, serverAddress, serverPort);

Parameters:

Parameter	Type	Description
identifier	const std::string&	Unique client identifier (e.g. "node0"). Must match NSBSimClient identifier in Per-Node mode.
serverAddress	std::string&	IP address or hostname of the NSB Daemon.
serverPort	int	Port number of the NSB Daemon.

Construction behavior. Upon construction, the client connects to the daemon, sends INIT, receives system configuration, and optionally connects to Redis.

send(dest_id, payload)

Sends a payload to a destination via NSB.

std::string key = nsb_conn.send(dest_id, payload);

Parameters:

Parameter	Type	Description
dest_id	const std::string	Identifier of the destination application client.
payload	std::string	The payload data to send.

Returns: std::string — Redis key for stored message (if database is configured), otherwise empty string.

Behavior: Fire-and-forget. Creates a SEND message and transmits to daemon. Daemon routes to simulator.

Example:

std::string payload = "Hello, World!";
nsb_conn.send("node1", payload);

receive()

Receives a payload via NSB.

// Default — receive for self, with default timeout
MessageEntry entry = nsb_conn.receive();

// With explicit destination and timeout
MessageEntry entry = nsb_conn.receive(&dest_id, timeout);

// With timeout only
MessageEntry entry = nsb_conn.receive(timeout);

Signatures:

MessageEntry receive(std::string* destId, int timeout = DAEMON_RESPONSE_TIMEOUT);
MessageEntry receive(int timeout = DAEMON_RESPONSE_TIMEOUT);

Parameters:

Parameter	Type	Default	Description
destId	std::string*	nullptr	Pointer to destination identifier. Pass nullptr to receive for self.
timeout	int	DAEMON_RESPONSE_TIMEOUT (30s)	Seconds to wait. Use 0 for non-blocking poll.

Returns: MessageEntry — Populated if message found; call exists() to check.

Behavior by mode:

• PULL mode: Sends RECEIVE request to daemon. Daemon responds with MESSAGE or NO_MESSAGE.
• PUSH mode: Waits on RECV channel using select with given timeout. Use timeout=0 for polling.

Example:

MessageEntry entry = nsb_conn.receive();
if (entry.exists()) {
    std::string payload = entry.payload_obj;
    // process...
}

listenReceive()

Blocking listener — for use in dedicated listener threads.

MessageEntry entry = nsb_conn.listenReceive();

Returns: MessageEntry

Purpose: Designed for a dedicated thread that blocks waiting for the next incoming payload, as an alternative to polling receive() in a loop.

Go Deeper

• MessageEntry — the struct returned by receive()
• NSBSimClient — the simulator-side counterpart, plus complete app/sim examples
• Python NSBAppClient — the equivalent class in Python