Give up a connect after connectTimeout instead of waiting the OS out

src/client.ts

@@ -22,6 +22,7 @@ export type ClientOptions = {
 	addrNpi?: number;
 	addrTon?: number;
 	bindType?: BindType;
+	connectTimeout?: number;
 	enquireLinkInterval?: number;
 	host?: string;
 	idleTimeout?: number;
@@ -52,7 +53,22 @@ const defaults = {
 	username: 'user',
 } as const;
 
+function armConnectTimeout(
+	sock: Socket,
+	connectTimeout: number | undefined,
+	settle: (result: Result<{ sock: Socket }>) => void,
+): NodeJS.Timeout | undefined {
+	if (connectTimeout === undefined) return undefined;
+
+	// The connecting socket is what holds the process, so this wait never has to.
+	return setTimeout(() => {
+		sock.destroy();
+		settle({ err: new Error(`Timed out connecting after ${String(connectTimeout)} ms`) });
+	}, connectTimeout).unref();
+}
+
 function openSocket(options: ClientOptions): Promise<Result<{ sock: Socket }>> {
+	const connectTimeout = options.connectTimeout;
 	const host = options.host ?? defaults.host;
 	const port = options.port ?? defaults.port;
 	const secure = options.tls !== undefined && options.tls !== false;
@@ -78,6 +94,8 @@ function openSocket(options: ClientOptions): Promise<Result<{ sock: Socket }>> {
 		}
 
 		const settle = (result: Result<{ sock: Socket }>): void => {
+			if (timer) clearTimeout(timer);
+
 			sock.removeListener('error', onError);
 			signal?.removeEventListener('abort', onAbort);
 			resolve(result);
@@ -97,6 +115,8 @@ function openSocket(options: ClientOptions): Promise<Result<{ sock: Socket }>> {
 		sock.once(secure ? 'secureConnect' : 'connect', () => {
 			settle({ sock });
 		});
+
+		const timer = armConnectTimeout(sock, connectTimeout, settle);
 	});
 }
 

src/session-options.ts

@@ -144,14 +144,11 @@ export function checkSessionOptions(options: CheckableOptions): VoidResult {
 		return { err: new Error('fromStart is part of the reconnect policy, spell it reconnect: { fromStart: true }') };
 	}
 
-	const checked = checkLimits([
-		['idleTimeout', options.idleTimeout ?? 0, 0],
-		['maxOutstanding', options.maxOutstanding ?? defaults.maxOutstanding, 1],
-		['maxReassembly', options.maxReassembly ?? defaults.maxReassembly, 1],
-		['reassemblyTimeout', options.reassemblyTimeout ?? defaults.reassemblyTimeout, 0],
-		['responseTimeout', options.responseTimeout ?? defaults.responseTimeout, 0],
-		['shutdownTimeout', options.shutdownTimeout ?? defaults.shutdownTimeout, 0],
-	]);
+	const connect = checkConnectTimeout(options.connectTimeout);
+
+	if (connect.err) return connect;
+
+	const checked = checkLimits(limitsOf(options));
 
 	if (checked.err) return checked;
 
@@ -160,6 +157,28 @@ export function checkSessionOptions(options: CheckableOptions): VoidResult {
 	return backoff.err ? backoff : checkSmsIdFormat(options.smsIdFormat);
 }
 
+function limitsOf(options: CheckableOptions): [string, number, number][] {
+	return [
+		['idleTimeout', options.idleTimeout ?? 0, 0],
+		['maxOutstanding', options.maxOutstanding ?? defaults.maxOutstanding, 1],
+		['maxReassembly', options.maxReassembly ?? defaults.maxReassembly, 1],
+		['reassemblyTimeout', options.reassemblyTimeout ?? defaults.reassemblyTimeout, 0],
+		['responseTimeout', options.responseTimeout ?? defaults.responseTimeout, 0],
+		['shutdownTimeout', options.shutdownTimeout ?? defaults.shutdownTimeout, 0],
+	];
+}
+
+/** Leaving it out is how the wait stays the OS's, so 0 would be a second spelling for that. */
+function checkConnectTimeout(connectTimeout: number | undefined): VoidResult {
+	if (connectTimeout === undefined) return {};
+
+	if (Number.isInteger(connectTimeout) && connectTimeout >= 1) return {};
+
+	const got = String(connectTimeout);
+
+	return { err: new Error(`connectTimeout must be 1 or more, got ${got}; omit it to wait the OS out`) };
+}
+
 function checkLimits(limits: [string, number, number][]): VoidResult {
 	for (const [name, value, min] of limits) {
 		if (!Number.isInteger(value) || value < min) {
@@ -238,6 +257,7 @@ function checkSmsIdFormat(smsIdFormat: unknown): VoidResult {
 
 /** What the checker reads, as it arrives: a caller without types can put anything in it. */
 export type CheckableOptions = {
+	connectTimeout?: number | undefined;
 	/** Not an option: the one spelling is inside reconnect, and this is where the other is refused. */
 	fromStart?: unknown;
 	idleTimeout?: number | undefined;