Set TCP_NODELAY on P2P sockets.

Nagle appears to be a significant contributor to latency now that the static
 sleeps are gone.  Most of our messages are relatively large compared to
 IP + TCP so I do not expect this to create enormous overhead.

This may also reduce traffic burstyness somewhat.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 87c4f0af0a..58b946f4a1 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -963,6 +963,15 @@ static void AcceptConnection(const ListenSocket& hListenSocket) {
         return;
     }
 
+    // According to the internet TCP_NODELAY is not carried into accepted sockets
+    // on all platforms.  Set it again here just to be sure.
+    int set = 1;
+#ifdef WIN32
+    setsockopt(hSocket, IPPROTO_TCP, TCP_NODELAY, (const char*)&set, sizeof(int));
+#else
+    setsockopt(hSocket, IPPROTO_TCP, TCP_NODELAY, (void*)&set, sizeof(int));
+#endif
+
     if (CNode::IsBanned(addr) && !whitelisted)
     {
         LogPrintf("connection from %s dropped (banned)\n", addr.ToString());
@@ -1790,8 +1799,11 @@ bool BindListenPort(const CService &addrBind, string& strError, bool fWhiteliste
     // Allow binding if the port is still in TIME_WAIT state after
     // the program was closed and restarted.
     setsockopt(hListenSocket, SOL_SOCKET, SO_REUSEADDR, (void*)&nOne, sizeof(int));
+    // Disable Nagle's algorithm
+    setsockopt(hListenSocket, IPPROTO_TCP, TCP_NODELAY, (void*)&nOne, sizeof(int));
 #else
     setsockopt(hListenSocket, SOL_SOCKET, SO_REUSEADDR, (const char*)&nOne, sizeof(int));
+    setsockopt(hListenSocket, IPPROTO_TCP, TCP_NODELAY, (const char*)&nOne, sizeof(int));
 #endif
 
     // Set to non-blocking, incoming connections will also inherit this