Fixed a bug with Letsencrypt certs

One of internal buffers was too small

src/stratum_server.cpp

@@ -58,7 +58,8 @@ StratumServer::StratumServer(p2pool* pool)
 	, m_totalFailedShares(0)
 	, m_apiLastUpdateTime(0)
 {
-	m_callbackBuf.resize(STRATUM_BUF_SIZE);
+	// Need a bigger buffer for the TLS handshake
+	m_callbackBuf.resize(STRATUM_CALLBACK_BUF_SIZE);
 
 	// Diffuse the initial state in case it has low quality
 	m_rng.discard(10000);

src/stratum_server.h

@@ -26,6 +26,7 @@ class p2pool;
 class BlockTemplate;
 
 static constexpr size_t STRATUM_BUF_SIZE = log::Stream::BUF_SIZE + 1;
+static constexpr size_t STRATUM_CALLBACK_BUF_SIZE = 16384;
 static constexpr int DEFAULT_STRATUM_PORT = 3333;
 
 class StratumServer : public TCPServer