P2PServer: show an error when there are no connections

src/log.h

@@ -371,6 +371,7 @@ template<> struct log::Stream::Entry<XMRAmount>
 
 template<> struct log::Stream::Entry<NetworkType>
 {
+	// cppcheck-suppress constParameter
 	static NOINLINE void put(const NetworkType& value, Stream* wrapper)
 	{
 		switch (value) {

src/p2p_server.cpp

@@ -49,6 +49,7 @@ P2PServer::P2PServer(p2pool* pool)
 	, m_rng(m_rd())
 	, m_block(new PoolBlock())
 	, m_timer{}
+	, m_timerCounter(0)
 	, m_peerId(m_rng())
 	, m_peerListLastSaved(0)
 {
@@ -227,6 +228,10 @@ void P2PServer::update_peer_connections()
 		}
 		peer_list.pop_back();
 	}
+
+	if ((m_numConnections == 0) && ((m_timerCounter % 30) == 0)) {
+		LOGERR(1, "no connections to other p2pool nodes, check your monerod/p2pool/network/firewall setup!!!");
+	}
 }
 
 void P2PServer::update_peer_list()
@@ -662,6 +667,8 @@ void P2PServer::print_status()
 
 void P2PServer::on_timer()
 {
+	++m_timerCounter;
+
 	if (!m_initialPeerList.empty()) {
 		connect_to_peers(m_initialPeerList);
 		m_initialPeerList.clear();

src/p2p_server.h

@@ -156,6 +156,7 @@ private:
 	PoolBlock* m_block;
 
 	uv_timer_t m_timer;
+	uint32_t m_timerCounter;
 
 	uint64_t m_peerId;