Networking

The net namespace provides TCP and UDP socket operations, DNS resolution, and socket timeouts. All functions support both IPv4 and IPv6.

TCP Client

let sock = net.connect("localhost", 5432)
net.send(sock, "hello")
let response = net.recv(sock)
print(response)
net.close(sock)

TCP Server

let server = net.listen(9000)
print("listening on 9000")

while (true) {
    let client = net.accept(server)
    let data = net.recv(client)
    net.send(client, "echo: " + data)
    net.close(client)
}

UDP

// Send a UDP datagram
let sock = net.udp()
net.sendTo(sock, "127.0.0.1", 9999, "hello udp")
net.close(sock)

// Listen for UDP datagrams
let server = net.udpBind(9999)
let msg = net.recvFrom(server)
print(msg.data, "from", msg.host, msg.port)
net.close(server)

DNS Resolution

let ips = net.resolve("example.com")
print(ips)    // ["93.184.216.34", "2606:2800:..."]

Socket Timeouts

let sock = net.connect("localhost", 8080)
net.setTimeout(sock, 5000)     // 5 second timeout

Function reference

TCP

Function	Description
net.connect(host, port)	Connect to a TCP server, returns socket
net.listen(port)	Bind and listen on a port, returns server socket
net.accept(server)	Accept a connection, returns client socket
net.send(sock, data)	Send a string, returns bytes sent
net.recv(sock, maxBytes?)	Receive data (default 4096 bytes), returns string
net.recvAll(sock)	Read until connection closes, returns string

UDP

Function	Description
net.udp()	Create an IPv4 UDP socket
net.udp6()	Create an IPv6 UDP socket
net.udpBind(port)	Create and bind a UDP socket to a port
net.sendTo(sock, host, port, data)	Send a UDP datagram
net.recvFrom(sock, maxBytes?)	Receive a datagram, returns {data, host, port}

Raw sockets

Function	Description
net.rawSocket(protocol)	Create a raw socket ("icmp", "tcp", "udp", etc.)
net.rawSend(sock, host, data)	Send raw data to a host
net.rawRecv(sock, maxBytes?)	Receive raw data, returns {data, host}

Raw sockets require root or CAP_NET_RAW on Linux. On macOS, unprivileged ICMP echo is supported via a SOCK_DGRAM fallback.

General

Function	Description
net.resolve(host)	DNS lookup, returns array of IP strings
net.setTimeout(sock, ms)	Set send/recv timeout in milliseconds
net.close(sock)	Close a socket

Example: ICMP ping

if (!sys.isRoot()) {
    print("warning: raw sockets may need root")
}

let sock = net.rawSocket("icmp")
net.setTimeout(sock, 2000)

let packet = bytes.pack(">BBHHh", [8, 0, 0, 1, 1])
net.rawSend(sock, "127.0.0.1", packet)
let reply = net.rawRecv(sock)
print("reply from:", reply.host)
net.close(sock)