fix: update server initialization to support preferred port and persist last used port

ios/Thefeed/ServerController.swift

@@ -33,13 +33,16 @@ final class ServerController: ObservableObject {
         guard instance == nil else { return }
         do {
             let dir = try Self.dataDir()
+            let saved = UserDefaults.standard.integer(forKey: "tf.lastPort")
             var err: NSError?
-            guard let s = MobileNewServer(dir.path, &err) else {
+            guard let s = MobileNewServer(dir.path, saved, &err) else {
                 lastError = err?.localizedDescription ?? "server start failed"
                 return
             }
             instance = s
-            port = Int(s.port())
+            let actual = Int(s.port())
+            port = actual
+            UserDefaults.standard.set(actual, forKey: "tf.lastPort")
             lastError = nil
         } catch {
             lastError = error.localizedDescription

mobile/mobile.go

@@ -7,6 +7,7 @@ package mobile
 import (
 	"errors"
 	"net"
+	"strconv"
 	"sync"
 
 	"github.com/sartoopjj/thefeed/internal/web"
@@ -24,15 +25,24 @@ type Server struct {
 	done    chan struct{}
 }
 
-// NewServer starts a server on a kernel-assigned port. dataDir must be
-// a writable, app-private directory (e.g. NSDocumentDirectory on iOS).
-func NewServer(dataDir string) (*Server, error) {
+// NewServer starts a server on 127.0.0.1. preferredPort=0 picks a
+// kernel-assigned port; a positive value is tried first and falls
+// back to kernel-assigned on bind failure. dataDir must be a writable
+// app-private directory (e.g. NSDocumentDirectory on iOS).
+func NewServer(dataDir string, preferredPort int) (*Server, error) {
 	if dataDir == "" {
 		return nil, errors.New("mobile: dataDir is empty")
 	}
-	ln, err := net.Listen("tcp", "127.0.0.1:0")
-	if err != nil {
-		return nil, err
+	var ln net.Listener
+	var err error
+	if preferredPort > 0 {
+		ln, err = net.Listen("tcp", net.JoinHostPort("127.0.0.1", strconv.Itoa(preferredPort)))
+	}
+	if ln == nil {
+		ln, err = net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			return nil, err
+		}
 	}
 	port := ln.Addr().(*net.TCPAddr).Port
 

mobile/mobile_test.go

@@ -10,14 +10,14 @@ import (
 )
 
 func TestNewServerEmptyDir(t *testing.T) {
-	if _, err := NewServer(""); err == nil {
+	if _, err := NewServer("", 0); err == nil {
 		t.Errorf("NewServer(\"\") succeeded, want error")
 	}
 }
 
 func TestServerLifecycle(t *testing.T) {
 	dir := t.TempDir()
-	s, err := NewServer(dir)
+	s, err := NewServer(dir, 0)
 	if err != nil {
 		t.Fatalf("NewServer: %v", err)
 	}
@@ -43,7 +43,7 @@ func TestServerLifecycle(t *testing.T) {
 }
 
 func TestStopIsIdempotent(t *testing.T) {
-	s, err := NewServer(t.TempDir())
+	s, err := NewServer(t.TempDir(), 0)
 	if err != nil {
 		t.Fatalf("NewServer: %v", err)
 	}
@@ -53,7 +53,7 @@ func TestStopIsIdempotent(t *testing.T) {
 
 func TestStopReleasesPort(t *testing.T) {
 	dir := t.TempDir()
-	s, err := NewServer(dir)
+	s, err := NewServer(dir, 0)
 	if err != nil {
 		t.Fatalf("NewServer: %v", err)
 	}