2 files changed, 11 insertions, 2 deletions
diff --git a/client.js b/client.js
index ebb2b66..e4a3427 100644
--- a/client.js
+++ b/client.js
@@ -16,10 +16,17 @@ const HOUR = 60 * 60 * 1000
 const _request = (pathOrUrl, opt, cb) => {
 	debug('_request', pathOrUrl, opt)
 
+	const {
+		verifyAlpnId,
+	} = {
+		verifyAlpnId: alpnId => alpnId === ALPN_ID,
+		...opt,
+	}
+
 	connect(opt, (err, socket) => {
 		if (err) return cb(err)
 
-		if (socket.alpnProtocol !== ALPN_ID) {
+		if (verifyAlpnId(socket.alpnProtocol) !== true) {
 			socket.destroy()
 			return cb(new Error('invalid or missing ALPN protocol'))
 		}
diff --git a/server.js b/server.js
index aa7afb7..88d3a2d 100644
--- a/server.js
+++ b/server.js
@@ -17,15 +17,17 @@ const createGeminiServer = (opt = {}, onRequest) => {
 	const {
 		cert, key, passphrase,
 		tlsOpt,
+		verifyAlpnId,
 	} = {
 		cert: null, key: null, passphrase: null,
 		tlsOpt: {},
+		verifyAlpnId: alpnId => alpnId === ALPN_ID,
 		...opt,
 	}
 
 	const onConnection = (socket) => {
 		// todo: clarify if this is desired behavior
-		if (socket.alpnProtocol !== ALPN_ID) {
+		if (verifyAlpnId(socket.alpnProtocol) !== true) {
 			socket.destroy()
 			return;
 		}