From 69d6a420899dc7cbf0c3193e39553dbb2ebefc3f Mon Sep 17 00:00:00 2001
From: Robert Doebbelin <robert@quobyte.com>
Date: Fri, 26 Jun 2020 15:28:22 +0200
Subject: [PATCH] Fall back to IPv4 if IPv6 is not supported

---
 server_http.hpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/server_http.hpp b/server_http.hpp
index 0536e92..cc531c7 100644
--- a/server_http.hpp
+++ b/server_http.hpp
@@ -401,7 +401,16 @@ namespace SimpleWeb {
 
       if(!acceptor)
         acceptor = std::unique_ptr<asio::ip::tcp::acceptor>(new asio::ip::tcp::acceptor(*io_service));
-      acceptor->open(endpoint.protocol());
+      try {
+        acceptor->open(endpoint.protocol());
+      } catch (const system_error& error) {
+        if(error.code() == asio::error::address_family_not_supported && config.address.empty()) {
+          endpoint = asio::ip::tcp::endpoint(asio::ip::tcp::v4(), config.port);
+          acceptor->open(endpoint.protocol());
+        } else {
+          throw;
+        }
+      }
       acceptor->set_option(asio::socket_base::reuse_address(config.reuse_address));
       if(config.fast_open) {
 #if defined(__linux__) && defined(TCP_FASTOPEN)