diff --git a/src/engine_robust.cc b/src/engine_robust.cc
index b969bc9f6..00efd7447 100644
--- a/src/engine_robust.cc
+++ b/src/engine_robust.cc
@@ -17,18 +17,14 @@ void AllReduceRobust::AllReduce(void *sendrecvbuf_,
                                 size_t type_nbytes,
                                 size_t count,           
                                 ReduceFunction reducer) {
-  utils::LogPrintf("[%d] call AllReduce", rank);  
-  TryResetLinks();
-  utils::LogPrintf("[%d] start work", rank);  
   while (true) {
     ReturnType ret = TryAllReduce(sendrecvbuf_, type_nbytes, count, reducer);
     if (ret == kSuccess) return;
     if (ret == kSockError) {
       utils::Error("error occur during all reduce\n");
     }
-    utils::LogPrintf("[%d] receive except signal, start reset link", rank);
+    utils::LogPrintf("[%d] receive except signal, start reset link\n", rank);
     TryResetLinks();
-    //utils::Check(TryResetLinks() == kSuccess, "error when reset links");    
   }
   // TODO
 }
@@ -70,13 +66,13 @@ void AllReduceRobust::CheckPoint(const utils::ISerializable &model) {
  *         and some link recovery proceduer is needed
  */
 AllReduceRobust::ReturnType AllReduceRobust::TryResetLinks(void) {
-  utils::LogPrintf("[%d] TryResetLinks, start\n", rank);
   // number of links
   const int nlink = static_cast<int>(links.size());
   for (int i = 0; i < nlink; ++i) {
     links[i].InitBuffer(sizeof(int), 1 << 10, reduce_buffer_size);
     links[i].ResetSize();
   }
+  
   // read and discard data from all channels until pass mark
   while (true) {
     for (int i = 0; i < nlink; ++i) {
@@ -92,20 +88,6 @@ AllReduceRobust::ReturnType AllReduceRobust::TryResetLinks(void) {
         ssize_t len = links[i].sock.Send(&sig, sizeof(sig));
         if (len == sizeof(sig)) links[i].size_write = 2;
       }
-      if (links[i].size_read == 0) {
-        int atmark = links[i].sock.AtMark();
-        if (atmark < 0) {
-          utils::Assert(links[i].sock.BadSocket(), "must already gone bad");
-        } else if (atmark > 0) {           
-          links[i].size_read = 1;
-        } else {
-          printf("buffer_size=%lu\n", links[i].buffer_size);
-          // no at mark, read and discard data
-          ssize_t len = links[i].sock.Recv(links[i].buffer_head, links[i].buffer_size);
-          // zero length, remote closed the connection, close socket
-          if (len == 0) links[i].sock.Close();
-        }
-      }
     }
     utils::SelectHelper rsel;
     bool finished = true;
@@ -113,15 +95,44 @@ AllReduceRobust::ReturnType AllReduceRobust::TryResetLinks(void) {
       if (links[i].size_write != 2 && !links[i].sock.BadSocket()) {
         rsel.WatchWrite(links[i].sock); finished = false;
       }
-      if (links[i].size_read == 0 && !links[i].sock.BadSocket()) {
-        rsel.WatchRead(links[i].sock); finished = false;
-      }
     }
     if (finished) break;
     // wait to read from the channels to discard data
     rsel.Select();
   }
-  utils::LogPrintf("[%d] Finish discard data\n", rank);
+  for (int i = 0; i < nlink; ++i) {
+    if (!links[i].sock.BadSocket()) {
+      utils::SelectHelper::WaitExcept(links[i].sock);
+    }
+  }
+  while (true) {
+    for (int i = 0; i < nlink; ++i) {
+      if (links[i].size_read == 0) {
+        int atmark = links[i].sock.AtMark();
+        if (atmark < 0) {
+          utils::Assert(links[i].sock.BadSocket(), "must already gone bad");
+        } else if (atmark > 0) {
+          links[i].size_read = 1;
+        } else {
+          // no at mark, read and discard data
+          ssize_t len = links[i].sock.Recv(links[i].buffer_head, links[i].buffer_size);
+          if (links[i].sock.AtMark()) links[i].size_read = 1;
+          // zero length, remote closed the connection, close socket
+          if (len == 0) links[i].sock.Close();
+        }
+      }
+    }
+    utils::SelectHelper rsel;
+    bool finished = true;    
+    for (int i = 0; i < nlink; ++i) {
+      if (links[i].size_read == 0 && !links[i].sock.BadSocket()) {
+        rsel.WatchRead(links[i].sock); finished = false;
+      }
+    }
+    if (finished) break;
+    rsel.Select();
+  }
+
   // start synchronization, use blocking I/O to avoid select
   for (int i = 0; i < nlink; ++i) {
     if (!links[i].sock.BadSocket()) {
@@ -132,7 +143,7 @@ AllReduceRobust::ReturnType AllReduceRobust::TryResetLinks(void) {
         links[i].sock.Close(); continue;
       } else if (len > 0) {
         utils::Assert(oob_mark == kResetMark, "wrong oob msg");
-        utils::Assert(!links[i].sock.AtMark(), "should already read past mark");
+        utils::Assert(links[i].sock.AtMark() != 1, "should already read past mark");
       } else {
         utils::Assert(errno != EAGAIN|| errno != EWOULDBLOCK, "BUG");
       }
@@ -147,7 +158,6 @@ AllReduceRobust::ReturnType AllReduceRobust::TryResetLinks(void) {
       }
     }
   }
-  utils::LogPrintf("[%d] GGet all Acks\n", rank);
   // wait all ack
   for (int i = 0; i < nlink; ++i) {
     if (!links[i].sock.BadSocket()) {
@@ -167,7 +177,6 @@ AllReduceRobust::ReturnType AllReduceRobust::TryResetLinks(void) {
   for (int i = 0; i < nlink; ++i) {
     if (links[i].sock.BadSocket()) return kSockError;
   }
-  utils::LogPrintf("[%d] TryResetLinks,!! return\n", rank);
   return kSuccess;
 }
 
diff --git a/src/socket.h b/src/socket.h
index a5238a6c0..8f6d969e6 100644
--- a/src/socket.h
+++ b/src/socket.h
@@ -177,7 +177,7 @@ class Socket {
   inline bool BadSocket(void) const {
     if (IsClosed()) return true;
     int err = GetSockError();
-    if (err == EBADF || err == EINTR) return true;
+    if (err == EBADF || err == EINTR) return true;    
     return false;
   }
   /*! \brief check if socket is already closed */
@@ -250,7 +250,7 @@ class TCPSocket : public Socket{
     int atmark;
 #ifdef _WIN32
     if (ioctlsocket(sockfd, SIOCATMARK, &atmark) != NO_ERROR) return -1;
-#else    
+#else
     if (ioctl(sockfd, SIOCATMARK, &atmark) == -1) return -1;
 #endif
     return atmark;
@@ -418,6 +418,7 @@ struct SelectHelper {
   
  private:
   inline static int Select_(int maxfd, fd_set *rfds, fd_set *wfds, fd_set *efds, long timeout) {
+    utils::Assert(maxfd < FD_SETSIZE, "maxdf must be smaller than FDSETSIZE");
     if (timeout == 0) {
       return select(maxfd, rfds, wfds, efds, NULL);
     } else {
diff --git a/src/utils.h b/src/utils.h
index 81bba7dfd..a371d6059 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -78,6 +78,7 @@ inline void HandlePrint(const char *msg) {
 }
 inline void HandleLogPrint(const char *msg) {
   fprintf(stderr, "%s", msg);
+  fflush(stderr);
 }
 #else
 #ifndef ALLREDUCE_STRICT_CXX98_