Revert "Implement a more robust IPC system between the launcher and client (#4159)"

This reverts commit 5ffcc48d75.

apps/app/src/api/oauth_utils/auth_code_reply.rs

@@ -11,7 +11,7 @@
 //! [RFC 8252]: https://datatracker.ietf.org/doc/html/rfc8252
 
 use std::{
-    net::SocketAddr,
+    net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr},
     sync::{LazyLock, Mutex},
     time::Duration,
 };
@@ -19,8 +19,10 @@ use std::{
 use hyper::body::Incoming;
 use hyper_util::rt::{TokioIo, TokioTimer};
 use theseus::ErrorKind;
-use theseus::prelude::tcp_listen_any_loopback;
-use tokio::sync::{broadcast, oneshot};
+use tokio::{
+    net::TcpListener,
+    sync::{broadcast, oneshot},
+};
 
 static SERVER_SHUTDOWN: LazyLock<broadcast::Sender<()>> =
     LazyLock::new(|| broadcast::channel(1024).0);
@@ -33,7 +35,17 @@ static SERVER_SHUTDOWN: LazyLock<broadcast::Sender<()>> =
 pub async fn listen(
     listen_socket_tx: oneshot::Sender<Result<SocketAddr, theseus::Error>>,
 ) -> Result<Option<String>, theseus::Error> {
-    let listener = match tcp_listen_any_loopback().await {
+    // IPv4 is tried first for the best compatibility and performance with most systems.
+    // IPv6 is also tried in case IPv4 is not available. Resolving "localhost" is avoided
+    // to prevent failures deriving from improper name resolution setup. Any available
+    // ephemeral port is used to prevent conflicts with other services. This is all as per
+    // RFC 8252's recommendations
+    const ANY_LOOPBACK_SOCKET: &[SocketAddr] = &[
+        SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 0),
+        SocketAddr::new(IpAddr::V6(Ipv6Addr::LOCALHOST), 0),
+    ];
+
+    let listener = match TcpListener::bind(ANY_LOOPBACK_SOCKET).await {
         Ok(listener) => {
             listen_socket_tx
                 .send(listener.local_addr().map_err(|e| {