net TCP communication

net.listen({type: 'tcp'}) starts the TCP server, net.connect({type: 'tcp'}) creates the TCP client.

net.listen({type: 'tcp', ...}) uses the following fields:

Field	Type	Required	Default value	Description
type	String	Yes	None	Fixed to `tcp`.
bind	String	Yes	None	TCP listening address in `host:port` format, for example `127.0.0.1:9000`. When the port is `0`, the operating system allocates an available port.
binary	Bool	No	false	When true, the message parameter of on_message returns Bytes; the default behavior is to maintain String compatibility.
on_connect	Fn	No	None	Called when the client connection is successful, the callback parameter is `client`.
on_message	Fn	No	None	Called when client data is received, the callback parameter is `client, message`.
on_close	Fn	No	None	Called when the client connection is closed, the callback parameter is `client`.
on_error	Fn	No	None	Called when there is an error in server monitoring or connection processing, the callback parameter is `message`.

net.connect({type: 'tcp', ...}) uses the following fields:

Field	Type	Required	Default	Description
type	String	Yes	None	Fixed to `tcp`.
host	String	Yes	None	TCP server host name or IP address.
port	Int	Yes	None	TCP server port number.
timeout	Int	No	`0`	Connection, read, and write timeout, in milliseconds; less than or equal to 0 means no timeout is set.

Type	Description
TcpServer	The TCP server handle returned by `net.listen({type:'tcp'})`.
TcpClient	The TCP client handle returned by `net.connect({type:'tcp'})` will also be used as the client parameter in the server callback.

Name	Type	Description
addr	String	The actual listening address, the format is usually `host:port`; when the bind port is 0, the port allocated by the system can be read from here.
type	String	Fixed to `tcp`.
close()	Fn -> Bool	Close TCP server monitoring, return true successfully.

Name	Type	Description
addr	String	The remote address of the client connection, usually in the format `host:port`.
type	String	Fixed to `tcp`.
write(data)	Fn -> Int	Write to String, byte array or Bytes and return the number of bytes written.
send(data)	Fn -> Int	Synonymous method for `write(data)`.
read()	Fn -> String	Synchronously read a piece of data and convert it to a string according to UTF-8 lossy; used for clients created by `net.connect`.
read_bytes()	Fn -> Bytes	Synchronously read a segment of raw bytes; used for clients created by `net.connect`.
close()	Fn -> Bool	Close the TCP connection and return true on success.

Callback	Parameter	Description
on_connect	client: TcpClient	Triggered when the new client connection is successful.
on_message	client: TcpClient, message: String/Bytes	Triggered when client data is received; when `binary: true`, message is Bytes, otherwise it is a compatible string.
on_close	client: TcpClient	Triggered when the client connection is closed.
on_error	message: String	Triggered when the server or connection handles errors.

The on_message callback parameters are client and message. The default message is a string converted by UTF-8 lossy; it is Bytes when the monitoring configuration is binary: true.
write/send returns the number of bytes written. read returns a string and read_bytes returns Bytes.
The client in the server-side on_connect/on_message/on_close callback is driven by the background read task and should receive data through on_message. Do not call client.read() to double read the same connection.
TCP server accept, connection read and write scheduling use the shared Tokio runtime, no longer creating independent read threads for each connection.
A single read and write message is limited by BT_NET_MESSAGE_LIMIT and defaults to 1048576 bytes.
Connection writes in the server callback will enter the single-connection bounded write queue. The queue length is controlled by BT_NET_WRITE_QUEUE and defaults to 1024.
When the network event queue is full, the TCP message event will trigger the connection to be closed and BT.stats().net.event_queue_rejected will be added.
When BT_NET_IDLE_TTL_MS is greater than 0, if the server connection does not receive data for more than this time, an error callback will be triggered and closed.