---
title: "Open TCP Port Not Recognized By Router"
url: "https://maker.wiznet.io/forum/12396"
markdown_url: "https://maker.wiznet.io/forum/12396/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "BitBanger46"
created: "2017-07-26T02:20:08+09:00"
last_activity: "2017-07-27T06:24:00+09:00"
language: "en"
views: 916
replies: 2
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Open TCP Port Not Recognized By Router

## Question

Asked by BitBanger46 on 2017-07-26 in Ethernet Chips.

I have designed over a dozen boards that use the W5500 for TCP communications over a LAN. I recently tried to access the W5500 on a board which was configured in TCP mode and was in the Listen state. If I use a browser (like IE11) over the LAN, there is no problem connecting to port 80 of the W5500. However, if I set up my Netgear FV318 router for port forwarding to port 80 of the same W5500, the router does not recognize that the port is open!!

I spent considerable time (and money) working with the tech support people at Netgear to verify that the problem was with the W5500 and not the router.

I further confirmed this problem when I attempted to connect to the W5500 through the LAN using an ESP-8266 Wi-Fi device. The ESP-8266 successfully connects to an IP camera on the LAN but fails to connect to the W5500 on the same LAN.

I would like to find someone who has anyone successfully used port forwarding with the W5500 as the target device.

## Replies

### Reply 1 by Eugeny, 2017-07-26

As long as you were talking to support, you most probably have much more technical information about the incident. Can you share it please? Did you investigate packets and their flow?

### Reply 2 by jim, 2017-07-27 (in reply to reply 1)

Please check steps below.

1. If you don’t use DHCP in a target, change to DHCP.
   And then check the status of target in a router.

2. After No. 1, if a target isn’t recognized in a router, you must have the connection of TCP between a target to external IP once. In this case, it doesn’t matter DHCP or Static IP. Please check the status of target in a router.

3. After No.2, if you can recognize a target in a router, and then please use port forward function in a router.

In my case, I used a WIZ550SR-EVB and ipTIME-A2004plus router. I succeeded.

![](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/b/b8d6e2dcd5bec247883a5bcb23ffd889e5204557.png) [wiznet.io](https://www.wiznet.io/product-item/wiz550sr-evb/)

### [WIZ550SR-EVB | WIZnet Co., Ltd.](https://www.wiznet.io/product-item/wiz550sr-evb/)

Support fast evaluation & test of WIZ550S2E module and two types of base board for RS-232 & RS-422/485 interface

Thanks.

---

Source: https://maker.wiznet.io/forum/12396