server fix bind() when 5075 in use

src/server.cpp

@@ -305,10 +305,12 @@ Server::Pvt::Pvt(Config&& conf)
     acceptor_loop.call([this, &dummy](){
         // from acceptor worker
 
+        bool firstiface = true;
         for(const auto& addr : effective.interfaces) {
-            interfaces.emplace_back(addr, effective.tcp_port, this);
-            if(effective.tcp_port==0)
+            interfaces.emplace_back(addr, effective.tcp_port, this, firstiface);
+            if(firstiface || effective.tcp_port==0)
                 effective.tcp_port = interfaces.back().bind_addr.port();
+            firstiface = false;
         }
 
         for(const auto& addr : effective.beaconDestinations) {

src/serverconn.cpp

@@ -508,7 +508,7 @@ void ServerConn::bevWriteS(struct bufferevent *bev, void *ptr)
     }
 }
 
-ServIface::ServIface(const std::string& addr, unsigned short port, server::Server::Pvt *server)
+ServIface::ServIface(const std::string& addr, unsigned short port, server::Server::Pvt *server, bool fallback)
     :server(server)
     ,bind_addr(AF_INET, addr.c_str(), port)
     ,sock(AF_INET, SOCK_STREAM, 0)
@@ -520,7 +520,7 @@ ServIface::ServIface(const std::string& addr, unsigned short port, server::Serve
         try {
             sock.bind(bind_addr);
         } catch(std::system_error& e) {
-            if(e.code().value()==SOCK_EADDRINUSE && bind_addr.port()!=0) {
+            if(fallback && e.code().value()==SOCK_EADDRINUSE) {
                 bind_addr.setPort(0);
                 continue;
             }

src/serverconn.h

@@ -168,7 +168,7 @@ struct ServIface
     evsocket sock;
     evlisten listener;
 
-    ServIface(const std::string& addr, unsigned short port, server::Server::Pvt *server);
+    ServIface(const std::string& addr, unsigned short port, server::Server::Pvt *server, bool fallback);
 
     static void onConnS(struct evconnlistener *listener, evutil_socket_t sock, struct sockaddr *peer, int socklen, void *raw);
 };