diff --git a/guest/forwarder_guest_launcher/debian/service b/guest/forwarder_guest_launcher/debian/service
index ad57a26..7812d67 100644
--- a/guest/forwarder_guest_launcher/debian/service
+++ b/guest/forwarder_guest_launcher/debian/service
@@ -5,7 +5,7 @@
 After=virtiofs_internal.service
 
 [Service]
-ExecStart=/usr/bin/bash -c '/usr/bin/forwarder_guest_launcher --grpc_port $(cat /mnt/internal/debian_service_port)'
+ExecStart=/usr/bin/bash -c '/usr/bin/forwarder_guest_launcher --grpc-port-file /mnt/internal/debian_service_port'
 Type=simple
 Restart=on-failure
 RestartSec=1
diff --git a/guest/forwarder_guest_launcher/src/main.rs b/guest/forwarder_guest_launcher/src/main.rs
index f4c8ca9..3cb557a 100644
--- a/guest/forwarder_guest_launcher/src/main.rs
+++ b/guest/forwarder_guest_launcher/src/main.rs
@@ -52,10 +52,9 @@
 #[derive(Parser)]
 /// Flags for running command
 pub struct Args {
-    /// grpc port number
+    /// path to a file where grpc port number is written
     #[arg(long)]
-    #[arg(alias = "grpc_port")]
-    grpc_port: String,
+    grpc_port_file: String,
 }
 
 async fn process_forwarding_request_queue(
@@ -163,11 +162,23 @@
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    env_logger::init();
+    env_logger::builder().filter_level(log::LevelFilter::Debug).init();
     debug!("Starting forwarder_guest_launcher");
     let args = Args::parse();
     let gateway_ip_addr = netdev::get_default_gateway()?.ipv4[0];
-    let addr = format!("https://{}:{}", gateway_ip_addr.to_string(), args.grpc_port);
+
+    // Wait for `grpc_port_file` becomes available.
+    const GRPC_PORT_MAX_RETRY_COUNT: u32 = 10;
+    for _ in 0..GRPC_PORT_MAX_RETRY_COUNT {
+        if std::path::Path::new(&args.grpc_port_file).exists() {
+            break;
+        }
+        debug!("{} does not exist. Wait 1 second", args.grpc_port_file);
+        tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+    }
+    let grpc_port = std::fs::read_to_string(&args.grpc_port_file)?.trim().to_string();
+
+    let addr = format!("https://{}:{}", gateway_ip_addr.to_string(), grpc_port);
     let channel = Endpoint::from_shared(addr)?.connect().await?;
     let client = DebianServiceClient::new(channel);
 
diff --git a/guest/shutdown_runner/Cargo.toml b/guest/shutdown_runner/Cargo.toml
index 0b44baa..92f8762 100644
--- a/guest/shutdown_runner/Cargo.toml
+++ b/guest/shutdown_runner/Cargo.toml
@@ -7,6 +7,7 @@
 [dependencies]
 anyhow = "1.0.94"
 clap = { version = "4.5.20", features = ["derive"] }
+env_logger = "0.11.5"
 log = "0.4.22"
 netdev = "0.31.0"
 prost = "0.13.3"
diff --git a/guest/shutdown_runner/debian/service b/guest/shutdown_runner/debian/service
index 2668930..a5249d0 100644
--- a/guest/shutdown_runner/debian/service
+++ b/guest/shutdown_runner/debian/service
@@ -4,7 +4,7 @@
 After=virtiofs_internal.service
 
 [Service]
-ExecStart=/usr/bin/bash -c '/usr/bin/shutdown_runner --grpc_port $(cat /mnt/internal/debian_service_port)'
+ExecStart=/usr/bin/bash -c '/usr/bin/shutdown_runner --grpc-port-file /mnt/internal/debian_service_port'
 Type=simple
 Restart=on-failure
 RestartSec=1
diff --git a/guest/shutdown_runner/src/main.rs b/guest/shutdown_runner/src/main.rs
index 19e9883..4043002 100644
--- a/guest/shutdown_runner/src/main.rs
+++ b/guest/shutdown_runner/src/main.rs
@@ -1,3 +1,17 @@
+// Copyright 2024 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 use api::debian_service_client::DebianServiceClient;
 use api::ShutdownQueueOpeningRequest;
 use std::process::Command;
@@ -12,18 +26,28 @@
 #[derive(Parser)]
 /// Flags for running command
 pub struct Args {
-    /// grpc port number
+    /// Path to a file where grpc port number is written
     #[arg(long)]
-    #[arg(alias = "grpc_port")]
-    grpc_port: String,
+    grpc_port_file: String,
 }
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    env_logger::builder().filter_level(log::LevelFilter::Debug).init();
     let args = Args::parse();
     let gateway_ip_addr = netdev::get_default_gateway()?.ipv4[0];
 
-    let server_addr = format!("http://{}:{}", gateway_ip_addr.to_string(), args.grpc_port);
+    // Wait for `grpc_port_file` becomes available.
+    const GRPC_PORT_MAX_RETRY_COUNT: u32 = 10;
+    for _ in 0..GRPC_PORT_MAX_RETRY_COUNT {
+        if std::path::Path::new(&args.grpc_port_file).exists() {
+            break;
+        }
+        debug!("{} does not exist. Wait 1 second", args.grpc_port_file);
+        tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+    }
+    let grpc_port = std::fs::read_to_string(&args.grpc_port_file)?.trim().to_string();
+    let server_addr = format!("http://{}:{}", gateway_ip_addr.to_string(), grpc_port);
 
     debug!("connect to grpc server {}", server_addr);