diff --git a/config/config-sample.json b/config/config-sample.json
index 2253f78..b937a1b 100644
--- a/config/config-sample.json
+++ b/config/config-sample.json
@@ -6,7 +6,7 @@
   "NBI_PORT" : 7557,
   "FS_INTERFACE" : "0.0.0.0",
   "FS_PORT" : 7567,
-  "FS_HOSTNAME" : "acs.example.com",
+  "FS_HOSTNAME" : "",
   "UI_INTERFACE" : "0.0.0.0",
   "UI_PORT" : 3000,
   "UI_JWT_SECRET": ""
diff --git a/lib/config.ts b/lib/config.ts
index 4095e58..bd4c754 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -62,7 +62,7 @@ const options = {
   FS_INTERFACE: { type: "string", default: "0.0.0.0" },
   FS_SSL_CERT: { type: "string", default: "" },
   FS_SSL_KEY: { type: "string", default: "" },
-  FS_HOSTNAME: { type: "string", default: "acs.example.com" },
+  FS_HOSTNAME: { type: "string", default: "" },
   FS_LOG_FILE: { type: "path", default: "" },
   FS_ACCESS_LOG_FILE: { type: "path", default: "" },
 
diff --git a/lib/cwmp.ts b/lib/cwmp.ts
index b34f6e7..688c696 100644
--- a/lib/cwmp.ts
+++ b/lib/cwmp.ts
@@ -772,10 +772,15 @@ async function sendAcsRequest(
     downloadRequest.fileSize = 0;
     if (!downloadRequest.url) {
       const FS_PORT = config.get("FS_PORT");
-      const FS_HOSTNAME = config.get("FS_HOSTNAME");
       const FS_SSL = config.get("FS_SSL");
+      let hostname = config.get("FS_HOSTNAME");
+      if (!hostname) {
+        if (sessionContext.httpRequest.headers["host"])
+          hostname = sessionContext.httpRequest.headers["host"].split(":")[0];
+        else hostname = sessionContext.httpRequest.connection.localAddress;
+      }
       downloadRequest.url = FS_SSL ? "https://" : "http://";
-      downloadRequest.url += FS_HOSTNAME;
+      downloadRequest.url += hostname;
       if (FS_PORT !== 80) downloadRequest.url += ":" + FS_PORT;
       downloadRequest.url += "/" + encodeURI(downloadRequest.fileName);