#transport - shared connection-security mode

Import with import "transport.j" as transport;. A single shared enum for the connection security mode used by every network-client module that opens a socket - smtp, pop, imap, redis, amqp, mqtt. One typed value instead of a stringly-typed security field per module, so a typo is a compile-time error, not a silent plaintext downgrade. Pure .j (just an enum + one helper); runs on both binaries.

import "transport.j" as transport;
import "smtp.j" as smtp;

def o as smtp.Options init smtp.Options{
    host: "smtp.example.com", port: 587,
    security: transport.Security.Starttls,
    clientName: "me", user: "u", pass: "p", auth: "", allowInsecureAuth: false};

#The Security enum

export def enum transport.Security { None, Tls, Starttls };

The zero value is Security.None (the first variant), so a zero-value Options is plaintext.

Only the protocols with an in-band upgrade command accept Starttls: smtp, pop, and imap. redis, amqp, and mqtt have no such command and reject Security.Starttls with a catchable Error (their match handles the variant explicitly rather than silently treating it as plaintext) - use Security.Tls for the TLS-on-connect port instead.

#Helper

encrypted is the "is this connection protected?" test - e.g. smtp uses it to refuse sending SASL credentials over a None connection unless allowInsecureAuth is set.

#Received-data cap

transport.MAX_RECEIVED_BYTES (64 MiB) is the tree-wide ceiling on a single received payload, and transport.checkReceiveSize(n, what) enforces it: it raises a catchable Error{kind: "transport"} naming what when n is negative or over the cap. A wire client calls it on a peer-declared body / literal size before reading, and on an accumulating buffer's length inside a read loop, so a hostile or desynced server cannot drive the recover-less interpreter to an unbounded allocation. One shared constant and check, so the whole client suite caps identically instead of each module inventing its own.

def bodySize as int init decodeContentBodySize($frame);
transport.checkReceiveSize($bodySize, "amqp message body");   # throws if > 64 MiB

#Why a separate module

The security mode is the one field shared verbatim across every socket client, so it lives in one place rather than duplicated as six sibling enums (the one-way-per-thing stance). Because Jennifer has no re-export, a program that builds a client Options imports transport alongside the client module - the small cost of a single shared type.

#See also

• smtp.md / pop.md / imap.md - the mail clients (support all three modes).
• redis.md / amqp.md / mqtt.md - the store / broker clients (None / Tls).
• ldap.md - the LDAP client (None / Tls / Starttls).
• net.md - the TLS transport underneath.
• modules/index.md - the module catalog and import rules.