[Log] fix confusing error log in TCPSocket::Bind() (#4299)

* [Log] fix confusing error log in TCPSocket::Bind()

* fix lint

src/rpc/network/tcp_socket.cc

@@ -64,14 +64,22 @@ bool TCPSocket::Bind(const char * ip, int port) {
   SAI sa_server;
   sa_server.sin_family      = AF_INET;
   sa_server.sin_port        = htons(port);
-  int retval = 0;
+  int ret = 0;
+  ret = inet_pton(AF_INET, ip, &sa_server.sin_addr);
+  if (ret == 0) {
+    LOG(ERROR) << "Invalid IP: " << ip;
+    return false;
+  } else if (ret < 0) {
+    LOG(ERROR) << "Failed to convert [" << ip
+               << "] to binary form, error: " << strerror(errno);
+    return false;
+  }
   do {  // retry if EINTR failure appears
-    if (0 < inet_pton(AF_INET, ip, &sa_server.sin_addr) &&
-        0 <= (retval = bind(socket_, reinterpret_cast<SA*>(&sa_server),
-                  sizeof(sa_server)))) {
+    if (0 <= (ret = bind(socket_, reinterpret_cast<SA *>(&sa_server),
+                         sizeof(sa_server)))) {
       return true;
     }
-  } while (retval == -1 && errno == EINTR);
+  } while (ret == -1 && errno == EINTR);
 
   LOG(ERROR) << "Failed bind on " << ip << ":" << port << " , error: " << strerror(errno);
   return false;

tests/cpp/socket_communicator_test.cc

@@ -154,6 +154,14 @@ void start_server(int id) {
   receiver.Finalize();
 }
 
+TEST(SocketCommunicatorTest, TCPSocketBind) {
+  dgl::network::TCPSocket socket;
+  testing::internal::CaptureStderr();
+  EXPECT_EQ(socket.Bind("127.0.0", 50001), false);
+  const std::string stderr = testing::internal::GetCapturedStderr();
+  EXPECT_NE(stderr.find("Invalid IP: 127.0.0"), std::string::npos);
+}
+
 #else
 
 #include <windows.h>