Docs / Standard Library / Net

Net

The Net module provides TCP and UDP networking for Kit. It includes socket operations for both connection-oriented (TCP) and connectionless (UDP) protocols, enabling server and client network communication.

TCP Functions

The TCP functions provide connection-oriented socket networking.

Net.tcp-connect
String -> Int -> Result Int NetError
Connect to a TCP server at the given host and port. Returns a socket handle. 
match Net.tcp-connect "localhost" 8080
  | Ok socket -> println "Connected!"
  | Err e -> println "Connection failed: ${e}"
Net.tcp-listen
String -> Int -> Result Int NetError
Create a TCP server socket and listen for connections. Returns a listener socket handle. 
match Net.tcp-listen "0.0.0.0" 8080
  | Ok listener -> println "Listening on port 8080"
  | Err e -> println "Failed to bind: ${e}"
Net.tcp-accept
Int -> Result {socket: Int, address: String} NetError
Accept an incoming connection. Blocks until a client connects. Returns the client socket and address.
Net.tcp-send
Int -> String -> Result Int NetError
Send data over a connection. Returns the number of bytes sent.
Net.tcp-recv
Int -> Int -> Result String NetError
Receive up to max_bytes of data from a connection.
Net.tcp-recv-all
Int -> Result String NetError
Receive all data from a TCP socket until the connection closes.
Net.tcp-close
Int -> ()
Close a TCP socket.
Net.tcp-shutdown
Int -> String -> ()
Shutdown a TCP socket. Direction can be "read", "write", or "both".
Net.tcp-local-address
Int -> Option {host: String, port: Int}
Get the local address of a TCP socket.
Net.tcp-remote-address
Int -> Option {host: String, port: Int}
Get the remote address of a TCP socket.
Net.tcp-set-timeout
Int -> Int -> ()
Set the send and receive timeout for a TCP socket in milliseconds.
Net.tcp-set-nodelay
Int -> Bool -> ()
Enable or disable TCP_NODELAY (Nagle's algorithm). When enabled, data is sent immediately without buffering.

UDP Functions

The UDP functions provide connectionless datagram networking.

Net.udp-bind
String -> Int -> Result Int NetError
Create and bind a UDP socket to the specified host and port. Returns a socket handle. 
match Net.udp-bind "0.0.0.0" 9000
  | Ok socket -> println "UDP socket ready"
  | Err e -> println "Failed to bind: ${e}"
Net.udp-send-to
Int -> String -> String -> Result Int NetError
Send a datagram to the specified address. Address should be in "host:port" format.
Net.udp-recv-from
Int -> Int -> Result {data: String, address: String} NetError
Receive a datagram. Returns the data and sender's address.
Net.udp-connect
Int -> String -> Int -> Result () NetError
Associate a UDP socket with a specific remote address. After connecting, you can use udp-send and udp-recv.
Net.udp-send
Int -> String -> Result Int NetError
Send data on a connected UDP socket.
Net.udp-recv
Int -> Int -> Result String NetError
Receive data on a connected UDP socket.
Net.udp-close
Int -> ()
Close a UDP socket.
Net.udp-local-address
Int -> Option {host: String, port: Int}
Get the local address of a UDP socket.
Net.udp-set-broadcast
Int -> Bool -> ()
Enable or disable broadcast on a UDP socket.
Net.udp-set-timeout
Int -> Int -> ()
Set the send and receive timeout for a UDP socket in milliseconds.

Examples

TCP Echo Server

listener = match Net.tcp-listen "0.0.0.0" 8080
  | Ok sock -> sock
  | Err e ->
    println "Failed to start server: ${e}"
    exit 1

println "Echo server listening on port 8080"

loop = fn =>
  client = match Net.tcp-accept listener
    | Ok c -> c
    | Err e ->
      println "Accept failed: ${e}"
      exit 1

  match Net.tcp-recv client.socket 1024
    | Ok data ->
      Net.tcp-send client.socket data
      Net.tcp-close client.socket
    | Err _ ->
      Net.tcp-close client.socket

  loop()

loop()

TCP Client

socket = match Net.tcp-connect "localhost" 8080
  | Ok sock -> sock
  | Err e ->
    println "Connection failed: ${e}"
    exit 1

Net.tcp-send socket "Hello, server!"

match Net.tcp-recv socket 1024
  | Ok response ->
    println "Response: ${response}"
  | Err e ->
    println "Receive failed: ${e}"

Net.tcp-close socket

UDP Example

socket = match Net.udp-bind "0.0.0.0" 9000
  | Ok sock -> sock
  | Err e ->
    println "Failed to bind: ${e}"
    exit 1

Net.udp-send-to socket "localhost:9001" "Hello via UDP!"
Net.udp-close socket

Error Types

The Net module exports a NetError type for networking-specific errors. 

type NetError =
  | TCPListenError{message: String}
  | TCPConnectionError{message: String}
  | TCPAcceptError{message: String}
  | TCPSendError{message: String}
  | TCPRecvError{message: String}
  | UDPBindError{message: String}
  | UDPConnectionError{message: String}
  | UDPSendError{message: String}
  | UDPRecvError{message: String}
  | SocketError{message: String}

Handling Network Errors

match Net.tcp-connect "localhost" 8080
  | Ok socket -> println "Connected!"
  | Err (TCPConnectionError{message}) ->
      println "Connection error: ${message}"
  | Err (TCPSendError{message}) ->
      println "Send error: ${message}"
  | Err (TCPRecvError{message}) ->
      println "Receive error: ${message}"
  | Err e ->
      println "Error: ${e}"