---
title: "[W5500] TCP/IP 통신 관련 문의"
url: "https://maker.wiznet.io/forum/13043"
markdown_url: "https://maker.wiznet.io/forum/13043/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "simsim"
created: "2018-09-03T07:03:11+09:00"
last_activity: "2018-09-03T07:03:11+09:00"
language: "ko"
views: 687
replies: 0
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# [W5500] TCP/IP 통신 관련 문의

## Question

Asked by simsim on 2018-09-03 in Ethernet Chips.

안녕하세요.
W5500을 이용하여 TCP/IP 통신을 Client로 하고 있습니다.
평상시에는 동작이 잘되어 잘 사용하는데 가끔 서버에 연결을 못하는 문제가 발생하고 있습니다.
해당 문제 발생시 VPN에서 확인을 해본 결과 3-way-handshake가 이루어지지 않아서 세션 성립이 안된다고 합니다.
ack 패킷을 보내야하는데 syn, ack 패킷을 계속 보낸다고 합니다.
이에 대하여 혹시 예상되는 문제가 있으신가하여 문의드립니다.
아래 로그가 VPN쪽에서 분석한 로그입니다…

18:33:17.046249 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.450696 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.460418 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.460677 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.469523 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.470142 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.479463 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.479797 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.488728 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.489072 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.498566 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.498870 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.701016 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.710601 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.710994 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.720052 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.720249 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.729512 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.729709 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.739451 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.739644 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.748857 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:17.749054 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:17.951276 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2385229701, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:18.050365 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S], seq 2460477269, win 2048, options [mss 1460], length 0
18:33:18.252583 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S], seq 2460477269, win 2048, options [mss 1460], length 0
18:33:18.262161 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:18.262356 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2460477269, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:18.271094 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:18.271601 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2460477269, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:18.280628 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:18.280821 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2460477269, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:18.289769 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:18.289966 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2460477269, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:18.298886 IP 211.192.50.244.5500 > 192.168.4.137.5000: Flags [S.], seq 1427764726, ack 2304320923, win 65535, options [mss 1300], length 0
18:33:18.299097 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2460477269, ack 1427764727, win 2048, options [mss 1300], length 0
18:33:18.501328 IP 192.168.4.137.5000 > 211.192.50.244.5500: Flags [S.], seq 2460477269, ack 1427764727, win 2048, options [mss 1300], length 0

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Source: https://maker.wiznet.io/forum/13043