TCP Send (`tcp-out`)¶

Writes msg.payload to a TCP peer. The mode selector picks where the destination comes from: a msg.session handle attached upstream by tcp-in server, every active session of a sibling tcp-in (broadcast), or a fresh dial to a remote.

Inputs	Outputs
1	0

Modes¶

Mode	Destination source
`reply`	`msg.session` (set by an upstream `tcp-in` server).
`server-broadcast`	All currently-connected sessions whose owner matches the configured `targetTcpIn`.
`client`	Dialed to `host:port` (or `msg.host` / `msg.port`).

Configuration¶

Common¶

Field	Default	Description
`mode`	`reply`	One of `reply`, `server-broadcast`, `client`.
`appendDelimiter`	—	Bytes appended after `msg.payload` (JS-style escapes). Useful for `\n` framing.
`closeAfterSend`	`false`	Half-close the connection after writing.
`writeTimeout`	`10s`	Per-write deadline.

`server-broadcast` mode¶

Field	Description
`targetTcpIn`	Node ID of the `tcp-in` server whose sessions receive the broadcast.

Broadcast iterates sessions serially with a per-session writeTimeout. A slow peer cannot block delivery to others — its write fails after the deadline and the loop continues. Per-target errors are logged but do not stop the broadcast.

`client` mode¶

Field	Default	Description
`host`	—	Destination host. `msg.host` overrides.
`port`	—	Destination port. `msg.port` overrides.
`keepConnection`	`true`	Keep one connection across messages (recommended).
`dialTimeout`	`10s`	Connect timeout.
`outboundQueueSize`	`64`	Backpressure buffer when the persistent conn is reconnecting. Overflow → catchable error.
`tls`	—	See TLS configuration.

With keepConnection=true a single worker holds the connection open and drains messages from a bounded outbound channel. On disconnect it reconnects with exponential backoff. Messages enqueued during the down phase wait in the channel; overflow raises a catchable error rather than silently blocking — loud failure beats silent stall.

Incoming message¶

Field	Required	Description
`payload`	yes*	Body to send. `string` → UTF-8 bytes; `[]byte` / `[]int` → raw bytes; `nil` → empty write (only useful with `appendDelimiter`).
`session`	reply	The opaque handle from an upstream `tcp-in` server.
`host`, `port`	client	Override the configured destination.
`closeAfterSend`	optional	Per-message override.

(* payload may be empty when paired with appendDelimiter.)

Errors¶

All write failures are catchable — pair the node with a Catch node to react:

Cause	Error text
Missing `msg.session` (reply)	`tcp-out … : no session handle on msg.session`
Session already closed (reply)	`tcp-out … : flow: tcp session closed`
Dial failure (client)	`tcp-out … : dial host:port: …`
Write timeout / broken pipe	`tcp-out … : write: …`
Persistent client overflow	`tcp-out … : outbound queue full`

Examples¶

Echo-on-receive with line framing.

[tcp-in  server :7000 delim=\n] → [Function: uppercase] → [tcp-out reply append=\n]

Push notifications to every connected client.

[Inject 10s] → [Change set payload="heartbeat"] → [tcp-out broadcast → tcp-in :7000]

Persistent client to a downstream service.

[mqtt-in topic=ingest] → [Change …] → [tcp-out client device:9100 keepConnection=true]

TCP Send (tcp-out)¶