From cf281281836563f18b3e3ea77238f6d733f45f59 Mon Sep 17 00:00:00 2001
From: Pierluigi D'Andrea <mail@pierluigi.me>
Date: Fri, 9 Aug 2024 10:07:24 +0200
Subject: [PATCH 1/2] Reserve HTTP server port

---
 .../SBTUITestTunnelClient.m                   | 54 +++++++++++++++----
 1 file changed, 44 insertions(+), 10 deletions(-)

diff --git a/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m b/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m
index 7c10e8e..86dff87 100755
--- a/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m
+++ b/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m
@@ -1062,26 +1062,60 @@ - (int)findOpenPort
         addr.sin_family = AF_INET;
         addr.sin_port = 0;
         inet_aton("0.0.0.0", &addr.sin_addr);
-        int sock = socket(AF_INET, SOCK_STREAM, 0);
-        if (sock < 0) {
+        int server_sock = socket(AF_INET, SOCK_STREAM, 0);
+        if (server_sock < 0) {
             return -1;
         }
-        if (bind(sock, (struct sockaddr*) &addr, sizeof(addr)) != 0) {
+        if (bind(server_sock, (struct sockaddr*) &addr, sizeof(addr)) != 0) {
+            close(server_sock);
             return -2;
         }
-        if (getsockname(sock, (struct sockaddr*) &addr, &len) != 0) {
+        if (getsockname(server_sock, (struct sockaddr*) &addr, &len) != 0) {
+            close(server_sock);
             return -3;
         }
-        
-        if (addr.sin_port > 1023) {
-            return addr.sin_port;
-        } else {
+
+        in_port_t port = addr.sin_port;
+
+        if (port <= 1023) {
+            close(server_sock);
             NSLog(@"[SBTUITestTunnel] Invalid port assigned, trying again");
-            close(sock);
+            continue;
+        }
+
+        // Put the port in the TIME_WAIT state, to temporarily reserve it
+        if (listen(server_sock, 1)) {
+            close(server_sock);
+            return -4;
+        }
+
+        int client_sock = socket(AF_INET, SOCK_STREAM, 0);
+        if (client_sock < 0) {
+            close(server_sock);
+            return -5;
+        }
+
+        if (connect(client_sock, (struct sockaddr*) &addr, sizeof(addr))) {
+            close(server_sock);
+            close(client_sock);
+            return -6;
         }
+
+        int accept_sock = accept(server_sock, nil, nil);
+        if (accept_sock < 0) {
+            close(server_sock);
+            close(client_sock);
+            return -7;
+        }
+
+        close(server_sock);
+        close(client_sock);
+        close(accept_sock);
+
+        return port;
     }
 
-    return -4;
+    return -8;
 }
 
 #pragma mark - Error Helpers

From b2c7835cd79c3f32c5d00778267fd24c1fdd304e Mon Sep 17 00:00:00 2001
From: Pierluigi D'Andrea <mail@pierluigi.me>
Date: Fri, 9 Aug 2024 20:12:37 +0200
Subject: [PATCH 2/2] Explain the logic behind port reservation more in detail

---
 Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m b/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m
index 86dff87..a1cfd77 100755
--- a/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m
+++ b/Sources/SBTUITestTunnelClient/SBTUITestTunnelClient.m
@@ -1083,7 +1083,12 @@ - (int)findOpenPort
             continue;
         }
 
-        // Put the port in the TIME_WAIT state, to temporarily reserve it
+        // Attempt to reserve the port by putting it in TIME_WAIT state. During this time,
+        // the system prevents other applications from binding to the same port,
+        // to prevent packets meant for the recently closed connection from being
+        // misdirected to the new application. Since SBTWebServer is utilizing SO_REUSEADDR on the
+        // server socket, we can bind to the port even though it's in TIME_WAIT state,
+        // effectively reserving it for our own use until we close the server socket.
         if (listen(server_sock, 1)) {
             close(server_sock);
             return -4;