Add --http_port flag to localserv and update tests

Added support for specifying a fixed HTTP port in localserv via the --http_port flag.
Updated localserv_test.py to use this flag and find a free port via Python socket binding,
removing the Unix-specific os.pipe and pass_fds logic to improve Windows compatibility.

Author: google-labs-jules[bot]

src/localserv/localserv_main.cc

@@ -163,7 +163,7 @@ static struct llama_context* create_context(struct llama_model* model, const Cha
 }
 
 static void print_usage(const char* argv0) {
-  fprintf(stderr, "usage: %s --model <model_path> [--context_length <n>] [--o_http_port <filepath>]\n", argv0);
+  fprintf(stderr, "usage: %s --model <model_path> [--context_length <n>] [--o_http_port <filepath>] [--http_port <port>]\n", argv0);
 }
 
 static std::string extract_json_string(const std::string& json, const std::string& key) {
@@ -201,6 +201,7 @@ int main(int argc, char** argv) {
   GlobalScope global_scope;
   ChatOptions opt;
   std::string o_http_port_filepath;
+  int opt_http_port = -1;
 
   int argi = 1;
   while (argi < argc) {
@@ -225,6 +226,13 @@ int main(int argc, char** argv) {
         return 1;
       }
       o_http_port_filepath = argv[argi];
+    } else if (strcmp(argv[argi], "--http_port") == 0) {
+      argi += 1;
+      if (argi == argc) {
+        print_usage(argv[0]);
+        return 1;
+      }
+      opt_http_port = std::stoi(argv[argi]);
     } else {
       print_usage(argv[0]);
       return 1;
@@ -267,7 +275,9 @@ int main(int argc, char** argv) {
   int prev_len = 0;
 
   int port = 8080;
-  if (!o_http_port_filepath.empty()) {
+  if (opt_http_port != -1) {
+    port = opt_http_port;
+  } else if (!o_http_port_filepath.empty()) {
     port = 0;
   }
 

test/localserv/localserv_test.py

@@ -23,37 +23,23 @@ def main():
         print(f"Error: Could not find src directory: {src_dir}")
         sys.exit(1)
 
-    # Create pipe for port communication
-    r_fd, w_fd = os.pipe()
-    port_arg = f"/dev/fd/{w_fd}"
+    # Find a free port
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.bind(('localhost', 0))
+    port = s.getsockname()[1]
+    s.close()
+    print(f"Selected port {port}")
 
     # Start the server
-    cmd = [executable_path] + extra_args + ["--o_http_port", port_arg]
+    cmd = [executable_path] + extra_args + ["--http_port", str(port)]
     print(f"Starting server: {cmd} in {src_dir}")
     process = subprocess.Popen(
         cmd,
         cwd=src_dir,
         stdout=sys.stdout,
         stderr=sys.stderr,
-        pass_fds=(w_fd,),
     )
 
-    # Close write end in parent
-    os.close(w_fd)
-
-    # Read port from pipe
-    try:
-        with os.fdopen(r_fd, 'r') as f:
-            port_str = f.readline().strip()
-            if not port_str:
-                raise ValueError("Failed to read port from pipe")
-            port = int(port_str)
-            print(f"Server listening on port {port}")
-    except Exception as e:
-        print(f"Failed to read port: {e}")
-        process.terminate()
-        sys.exit(1)
-
     # Wait for server to start up (connect to the dynamic port)
     start_time = time.time()
     while time.time() - start_time < 20: