diff --git a/src/client.rs b/src/client.rs
index 02824c1..119fc87 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -60,15 +60,22 @@ impl Client {
                     .as_ref(),
                     move |result| match result {
                         Ok(connection) => {
-                            match Connection::from(network_address, connection, certificate) {
+                            match Connection::new_for(
+                                &connection,
+                                certificate.as_ref(),
+                                Some(&network_address),
+                            ) {
                                 Ok(result) => request_async(
                                     result,
                                     uri.to_string(),
                                     match priority {
-                                        Some(priority) => priority,
-                                        None => Priority::DEFAULT,
+                                        Some(priority) => Some(priority),
+                                        None => Some(Priority::DEFAULT),
+                                    },
+                                    match cancellable {
+                                        Some(ref cancellable) => Some(cancellable.clone()),
+                                        None => None::<Cancellable>,
                                     },
-                                    cancellable.unwrap(), // @TODO
                                     move |result| callback(result),
                                 ),
                                 Err(reason) => callback(Err(Error::Connection(reason))),
@@ -83,30 +90,36 @@ impl Client {
     }
 }
 
-// Private helpers
-
-fn request_async(
+/// Make new request for constructed `Connection`
+/// * callback with `Result`on success or `Error` on failure
+pub fn request_async(
     connection: Connection,
     query: String,
-    priority: Priority,
-    cancellable: Cancellable,
+    priority: Option<Priority>,
+    cancellable: Option<Cancellable>,
     callback: impl Fn(Result<Response, Error>) + 'static,
 ) {
     connection.stream().output_stream().write_bytes_async(
         &Bytes::from(format!("{query}\r\n").as_bytes()),
-        priority,
-        Some(&cancellable.clone()),
+        match priority {
+            Some(priority) => priority,
+            None => Priority::DEFAULT,
+        },
+        match cancellable {
+            Some(ref cancellable) => Some(cancellable.clone()),
+            None => None::<Cancellable>,
+        }
+        .as_ref(),
         move |result| match result {
-            Ok(_) => Response::from_request_async(
-                connection,
-                Some(priority),
-                Some(cancellable),
-                move |result| match result {
-                    Ok(response) => callback(Ok(response)),
-                    Err(reason) => callback(Err(Error::Response(reason))),
-                },
-            ),
-            Err(reason) => callback(Err(Error::Write(reason))),
+            Ok(_) => {
+                Response::from_request_async(connection, priority, cancellable, move |result| {
+                    callback(match result {
+                        Ok(response) => Ok(response),
+                        Err(reason) => Err(Error::Response(reason)),
+                    })
+                })
+            }
+            Err(reason) => callback(Err(Error::OutputStream(reason))),
         },
     );
 }
diff --git a/src/client/connection.rs b/src/client/connection.rs
index a86a85b..1dede2a 100644
--- a/src/client/connection.rs
+++ b/src/client/connection.rs
@@ -19,10 +19,10 @@ impl Connection {
     // Constructors
 
     /// Create new `Self`
-    pub fn from(
-        network_address: NetworkAddress, // @TODO struct cert as sni
-        socket_connection: SocketConnection,
-        certificate: Option<TlsCertificate>,
+    pub fn new_for(
+        socket_connection: &SocketConnection,
+        certificate: Option<&TlsCertificate>,
+        server_identity: Option<&NetworkAddress>,
     ) -> Result<Self, Error> {
         if socket_connection.is_closed() {
             return Err(Error::SocketConnectionClosed);
@@ -31,7 +31,7 @@ impl Connection {
         Ok(Self {
             socket_connection: socket_connection.clone(),
             tls_client_connection: match certificate {
-                Some(certificate) => match auth(network_address, socket_connection, certificate) {
+                Some(certificate) => match auth(socket_connection, certificate, server_identity) {
                     Ok(tls_client_connection) => Some(tls_client_connection),
                     Err(reason) => return Err(reason),
                 },
@@ -53,19 +53,19 @@ impl Connection {
 // Tools
 
 pub fn auth(
-    server_identity: NetworkAddress, // @TODO impl IsA<SocketConnectable> ?
-    socket_connection: SocketConnection,
-    certificate: TlsCertificate,
+    socket_connection: &SocketConnection,
+    certificate: &TlsCertificate,
+    server_identity: Option<&NetworkAddress>,
 ) -> Result<TlsClientConnection, Error> {
     if socket_connection.is_closed() {
         return Err(Error::SocketConnectionClosed);
     }
 
     // https://geminiprotocol.net/docs/protocol-specification.gmi#the-use-of-tls
-    match TlsClientConnection::new(&socket_connection, Some(&server_identity)) {
+    match TlsClientConnection::new(socket_connection, server_identity) {
         Ok(tls_client_connection) => {
             // https://geminiprotocol.net/docs/protocol-specification.gmi#client-certificates
-            tls_client_connection.set_certificate(&certificate);
+            tls_client_connection.set_certificate(certificate);
 
             // @TODO handle exceptions
             // https://geminiprotocol.net/docs/protocol-specification.gmi#closing-connections
diff --git a/src/client/error.rs b/src/client/error.rs
index 65771c0..b6df128 100644
--- a/src/client/error.rs
+++ b/src/client/error.rs
@@ -6,9 +6,9 @@ pub enum Error {
     Connectable(String),
     Connection(crate::client::connection::Error),
     NetworkAddress(crate::gio::network_address::Error),
+    OutputStream(glib::Error),
     Request(glib::Error),
     Response(crate::client::response::Error),
-    Write(glib::Error),
 }
 
 impl Display for Error {
@@ -26,15 +26,15 @@ impl Display for Error {
             Self::NetworkAddress(reason) => {
                 write!(f, "Network address error: {reason}")
             }
+            Self::OutputStream(reason) => {
+                write!(f, "Output stream error: {reason}")
+            }
             Self::Request(reason) => {
                 write!(f, "Request error: {reason}")
             }
             Self::Response(reason) => {
                 write!(f, "Response error: {reason}")
             }
-            Self::Write(reason) => {
-                write!(f, "I/O Write error: {reason}")
-            }
         }
     }
 }