diff --git a/Dockerfile b/Dockerfile
index b6f99ca539d077164c71d797a5ccda7b1b5c44ba..39af60966b6cab7d8b9e644f4ea658613f8ba518 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -30,7 +30,8 @@ RUN apt-get update && \
     python-numpy python-matplotlib gcc g++ \
     automake locales clang-format-3.8 swig doxygen cmake  \
     liblapack-dev liblapacke-dev libboost-dev \
-    clang-3.8 llvm-3.8 libclang-3.8-dev && \
+    clang-3.8 llvm-3.8 libclang-3.8-dev \
+    net-tools && \
     apt-get clean -y
 
 # Install Go
diff --git a/paddle/pserver/LightNetwork.cpp b/paddle/pserver/LightNetwork.cpp
index 8c8ba0a2e51b85bde0544c6780b07130336a6bdd..922f25734dee0a6db7fbcfcef3d29d2bad5b7858 100644
--- a/paddle/pserver/LightNetwork.cpp
+++ b/paddle/pserver/LightNetwork.cpp
@@ -383,20 +383,23 @@ void SocketClient::TcpClient(const std::string &serverAddr, int serverPort) {
   setOption(sockfd);
 
   /// Now connect to the server
-  int retry_second = 0;
-  int error = 0;
+  int retry_count = 0;
   do {
-    error = connect(sockfd, (sockaddr *)&serv_addr, sizeof(serv_addr));
-    if (error == ECONNREFUSED) {
+    if (connect(sockfd, (sockaddr *)&serv_addr, sizeof(serv_addr)) == 0) {
+      break;
+    }
+
+    if (errno == ECONNREFUSED) {
       LOG(WARNING) << "connection refused by pserver, try again!";
-      if (retry_second++ >= 7) {
+      if (retry_count++ >= 7) {
         LOG(FATAL) << "connection refused by pserver, maybe pserver failed!";
       }
       std::this_thread::sleep_for(std::chrono::seconds(1));
     } else {
-      PCHECK(error >= 0) << "ERROR connecting to " << serverAddr;
+      PCHECK(errno != 0) << "ERROR connecting to " << serverAddr << ":"
+                         << serverPort << "errorno: " << errno;
     }
-  } while (error == ECONNREFUSED);
+  } while (errno == ECONNREFUSED);
 
   channel_.reset(new SocketChannel(sockfd, serverAddr));
   tcpRdma_ = F_TCP;