Editing Test connectivity for the web service

Find the problem occurred: (1) local service at the server (localhost) (2) from LAN to server (3) from WAN to server

{{LanguageSwitcher | content = [[Test connectivity for the web service | EN]], [[網路服務連線測試 | 漢字]] }}

=== How to connect to the web service ===

If the service is the web server: 
* (1) Open the browser, (2) Type the address: {{kbd | key = <nowiki>http://127.0.0.1</nowiki> }} or {{kbd | key =<nowiki>http://the.domain</nowiki>}}

* Linux lynx command: 
*# (optional if lynx was not installed) {{kbd | key = <nowiki>yum install lynx</nowiki>}} for CentOS / {{kbd | key = <nowiki>sudo apt-get install lynx</nowiki>}} for Ubuntu<ref>[http://www.addictivetips.com/ubuntu-linux-tips/install-and-use-lynx-on-ubuntu/ Install and Use Lynx Browser on Ubuntu]</ref>
*# {{kbd | key = <nowiki>lynx http://127.0.0.1</nowiki>}} <ref>[http://lynx.isc.org/lynx2.8.7/lynx2-8-7/lynx_help/Lynx_users_guide.html Lynx Users Guide v2.8.7]</ref> for {{Linux}}

* telnet command
*# {{kbd | key = telnet 127.0.0.1 <PORT>}} e.g. {{kbd | key = telnet 127.0.0.1 80}} or {{kbd | key = telnet the.domain 80}}
*# (after telnet-ed the web 80 port, key in) {{kbd_plus | key1 = get | key2 = SPACE}}<ref>[http://www.simplescripts.de/http-check-port-80-telnet-command.htm HTTP Check Port 80 with the Telnet Command]</ref>

* curl<ref>[https://curl.se/docs/manpage.html curl - How To Use]</ref>: {{kbd | key = <nowiki>curl -vL http://IP:Port</nowiki>}}
** (optional if curl command was not installed) [https://help.ubidots.com/en/articles/2165289-learn-how-to-install-run-curl-on-windows-macosx-linux Learn how to install & run cURL on Windows/MacOSX/Linux | Ubidots Help Center]
** commands e.g. 
*** (1) Write output to <file> instead of stdout using {{kbd | key = <nowiki>curl -voL https://www.google.com</nowiki>}} 
*** (2) Write output to stdout using {{kbd | key = <nowiki>curl -vL https://www.google.com</nowiki>}} or {{kbd | key = <nowiki>curl -voL /dev/null https://www.google.com</nowiki>}}
*** (3) Write output to <file> with the remote file name using {{kbd | key = <nowiki>curl -vOL https://www.google.com/index.html</nowiki>}}
** If failed. It will show the message: "failed: Connection refused"

* Linux [https://www.gnu.org/software/wget/ wget] software e.g. {{kbd | key = <nowiki>wget https://www.google.com</nowiki>}}

* use the third-party website monitoring the services: [[Web Ping]] 

If the service is not the web server, use telnet instead
# (optional) [https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc771275(v=ws.10) Install Telnet Client | Microsoft Docs] on {{Win}}. [https://medium.com/@blackSource/bring-telnet-back-on-macos-high-sierra-11de98de1544 Bring telnet back on macOS high Sierra – Ayuth Mangmesap (blackSource) – Medium] on {{Mac}}
# {{kbd | key = telnet 127.0.0.1 <PORT>}} If failed to connect the web service. It will show the message: "telnet: Unable to connect to remote host: Connection refused"

Using alternative web services if the Python or Node.js was installed

* (for python 3.x) {{kbd | key=<nowiki>python -m http.server [port]</nowiki>}} (default port: 8000)<ref>[https://docs.python.org/3.8/library/http.server.html?highlight=http%20server#module-http.server http.server — HTTP servers — Python 3.8.1 documentation]</ref>
* (for Node.js) {{kbd | key=<nowiki>npx http-server [-p port]</nowiki>}} (default port: 8080)<ref>[https://github.com/http-party/http-server http-server: a simple static HTTP server]</ref>

== Test connectivity for the local web service ==
WAN &#9675; -------&gt; &#9675; LAN -------&gt; <span style="color:red">&#9679; server</span>

{{Tips}} If you has administrative permission to log into the server via SSH or Remote desktop service.

=== Check if your computer/server Is being assigned the IP Address ===

* {{Linux}}: (1) Check the IP Address. {{kbd | key = ifconfig}}. (2) Re-assign the IP Address and restart the networking service. {{kbd | key = service network restart}} for CentOS<ref>[http://askubuntu.com/questions/230698/how-to-restart-the-networking-service How to restart the networking service? - Ask Ubuntu]</ref>
* {{Win}}: Check the IP Address. {{kbd | key = ifconfig/all}} 
* More on [[Network problem]]

=== Check if web service has started successfully? ===
* Apache {{kbd | key = /etc/init.d/httpd status}} on CentOS7 <ref>[https://www.e2enetworks.com/help/knowledge-base/how-to-check-running-status-of-lamp-stack/ How to check running status of LAMP stack | E2E Networks Knowledgebase]</ref>
* nginx {{kbd | key = sudo service nginx status}} on CentOS7 
* Docker container {{kbd | key = docker ps}} to check if the container is running & expose the port<ref>[https://docs.docker.com/engine/reference/commandline/ps/ docker ps | Docker Documentation]</ref>

=== Check if MySQL has started successfully? ===
==== Using lsof command ==== 
* {{kbd | key = lsof -i:3306}} on {{Mac}} or {{Linux}}

The command lsof -i:3306 is used in Unix-like operating systems to list open files and the processes that opened them. Let's break down the command:

lsof: This stands for "List Open Files". It's a command-line utility that displays information about files opened by processes. In Unix and Linux, everything is treated as a file (including hardware devices, sockets, and directories), so lsof is a powerful tool for system administrators to monitor and troubleshoot system behavior.

-i: This option tells lsof to show only network files. In Unix and Linux, network connections are treated as files. The -i option can be used to filter connections based on the Internet address or network protocol.

:3306: This specifies the port number. Port 3306 is commonly used by MySQL, a popular database management system. By including :3306, you are asking lsof to list all network files (which includes socket connections) that are associated with port 3306.

Example output: localhost:mysql (LISTEN) means the MySQL has started successfully
<pre>
COMMAND     PID      USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
mysqld    93034 account   29u  IPv4 0xxxx      0t0  TCP localhost:mysql (LISTEN)
</pre>

==== Using ps command ==== 
* {{kbd | key = <nowiki>ps aux | grep mysql</nowiki>}} on {{Mac}}

Example output if MySQL has started successfully:
<pre>
_mysql           11083   0.3  0.2 409657280  31424   ??  Ss    2:12下午   0:01.07 /usr/local/mysql/bin/mysqld --user=_mysql --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data --plugin-dir=/usr/local/mysql/lib/plugin --log-error=/usr/local/mysql/data/mysqld.local.err --pid-file=/usr/local/mysql/data/mysqld.local.pid --keyring-file-data=/usr/local/mysql/keyring/keyring --early-plugin-load=keyring_file=keyring_file.so
ACCOUNT        12349   0.0  0.0 408645328   1648 s011  S+    2:14下午   0:00.00 grep mysql
</pre>

Example output if MySQL has NOT started successfully:
<pre>
ACCOUNT        12349   0.0  0.0 408645328   1648 s011  S+    2:14下午   0:00.00 grep mysql
</pre>

=== Check if a port was occupied by other process? ===
Check the port if used by other protocol
* [https://www.speedguide.net/ports.php SG TCP/IP Ports Database]
* [https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers List of TCP and UDP port numbers - Wikipedia]

[[Find process running on port]]

* {{Linux}} 
** [http://linux.die.net/man/1/nmap nmap] "Network exploration tool and security / port scanner." e.g. {{kbd | key = <nowiki>nmap -p 80,443 ip</nowiki>}}
** [http://linux.die.net/man/8/ss ss] "utility to investigate sockets" e.g. {{kbd | key = <nowiki>ss -tnlp | grep 80</nowiki>}} or using OR operator<ref>[http://www.thegeekstuff.com/2011/10/grep-or-and-not-operators/ 7 Linux Grep OR, Grep AND, Grep NOT Operator Examples]</ref> {{kbd | key = <nowiki>ss -tnlp | grep '80\|443'</nowiki>}}
** [http://linuxcommand.org/man_pages/ps1.html ps] List the current processes. Input {{kbd | key = <nowiki>ps -aux | grep "PORT_NUMBER"</nowiki>}} e.g. {{kbd | key = <nowiki>ps -aux | grep 443</nowiki>}}
** [https://docs.oracle.com/cd/E19504-01/802-5753/6i9g71m3i/index.html netstat Command] {{kbd | key=<nowiki>netstat -tulpn | grep LISTEN</nowiki>}} e.g. 
** [https://docs.docker.com/engine/reference/commandline/port/ docker port | Docker Documentation]

Example output of netstat command
<pre>
$ netstat -tulpn | grep LISTEN

tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      - 

// means the 80 port service is running
</pre>

* {{Win}} 
** Using the software [http://www.nirsoft.net/utils/cports.html CurrPorts] to check the process and port. e.g. Apache will not running if the 80 port was occupied by skype<ref>[http://stackoverflow.com/questions/4705005/how-to-solve-wamp-and-skype-conflict-on-windows-7 How to solve WAMP and Skype conflict on Windows 7? - Stack Overflow]</ref>.

=== Check if a port is blocked by browser ===
Check if a port is blocked by browser<ref>[https://blog.miniasp.com/post/2022/05/02/Dont-use-ERR_UNSAFE_PORT-for-your-website?fbclid=IwAR2y9D60H-j8-5T1zJixTU-L2ydbn7LgnWpG1v53fyaKCyuuqx2MqfU80fI 開發與部署網站時需注意不要使用到 ERR_UNSAFE_PORT 不安全的埠號 | The Will Will Web]</ref>
* {{Chrome}} [https://chromium.googlesource.com/chromium/src.git/+/refs/heads/master/net/base/port_util.cc#52 net/base/port_util.cc - chromium/src.git - Git at Google]
* [https://fetch.spec.whatwg.org/#port-blocking Fetch Standard] 2.9. Port blocking


=== Is the port opened for external users? ===
Check the OS firewall or protected by antivirus software

** {{Linux}}
*** [http://linux.die.net/man/8/iptables iptables]: (1) {{kbd | key = iptables -L}} to list all rules<ref>[http://wiki.centos.org/HowTos/Network/IPTables HowTos/Network/IPTables - CentOS Wiki]</ref> (2) rule with smaller line-number will override the rule with larger line-number<ref>[https://fedoraproject.org/wiki/How_to_edit_iptables_rules?rd=User_talk:Rforlot How to edit iptables rules - FedoraProject]</ref>
*** [https://fedoraproject.org/wiki/FirewallD FirewallD] rules: (1) {{kbd | key = <nowiki>sudo firewall-cmd --get-default-zone</nowiki>}} return 'public' (2) {{kbd | key = <nowiki>sudo firewall-cmd --list-all --zone=public</nowiki>}}<ref>[https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-using-firewalld-on-centos-7 How To Set Up a Firewall Using FirewallD on CentOS 7 | DigitalOcean]</ref> (3) Allow port with FirewallD
*** [http://linux.die.net/man/8/semanage SELinux Policy Management]:  (1) After installed {{kbd | key =policycoreutils-python}}<ref>[http://sharadchhetri.com/2014/10/07/semanage-command-found-centos-7-rhel-7/ semanage command not found on CentOS 7 and RHEL 7]</ref>, input {{kbd | key = <nowiki>semanage port -l</nowiki>}} to list open ports. (2) Allow port with semanage.
** {{Win}} [https://technet.microsoft.com/en-us/library/cc754274.aspx?f=255&MSPPError=-2147217396 Windows Firewall with Advanced Security] -> configure firewall rules
** protected by antivirus software?
* connect to localhost ex: {{kbd | key= telnet 127.0.0.1 23}} where 23 is the port number where the service running
** [https://technet.microsoft.com/en-us/library/cc771275(v=ws.10).aspx Install Telnet Client] on {{Win}}
** if the local service is web server, you can also try  {{kbd | key = <nowiki>lynx http://127.0.0.1</nowiki>}} for {{Linux}}
* double [[Testing#check_the_server.2Fservice_logs | check the server/service logs]]

== Test connectivity from LAN to the server ==
WAN &#9675; -------&gt; <span style="color:red">&#9679; LAN -------&gt; &#9679; server</span>

Testing on LAN (local network, subnet scope): The different servers between LAN or with the same ip class (ex: 1.2.3.*) and may not have the firewall limit. [https://en.wikipedia.org/wiki/Private_network Private network] / Private IP address

* Is the service alive? 
* Connect to the internal IP eg: {{kbd | key= telnet 172.18.0.1 23}} (1) IP start with 172.18... is [http://www.itcom.itd.umich.edu/backbone/umnet/privateIP.html Private IP Network Numbers] (2) where 23 is the port number where the service running
* If the local service is web server, you can also try to connect the internal IP e.g. {{kbd | key = <nowiki>lynx http://172.18.0.1</nowiki>}} for {{Linux}}
* Double [[Testing#check_the_server.2Fservice_logs | check the server/service logs]]
* Is the internal IP correct?

== Test connectivity from WAN to the remote server ==
<span style="color:red">WAN &#9679; -------&gt; &#9679; LAN -------&gt; &#9679; server</span>

We met the trouble on WAN (wide area network). If we do no have the administrative permission, the tests we can do as follows:
*  [http://downforeveryoneorjustme.com/ Down for everyone or just me?] more on [[Web_Ping#同時從世界各處測試網站連線 | Web Ping]]
* Switch to different ISP? Is hardware firewall enabled?
* Is gateway alive?
* Is DNS alive?
* Is the external IP correct? 
** If the firewall rule is IP specified, verify the IP if correct from [http://whatismyipaddress.com/ What Is My IP Address?] or web access log.
** Query the [http://ipinfo.io/ IP Address Details - ipinfo.io]. e.g. Input the command {{kbd | key = <nowiki>curl ipinfo.io/ip</nowiki>}}<ref>[https://askubuntu.com/questions/95910/command-for-determining-my-public-ip#comment1318649_95910 networking - Command for determining my public IP? - Ask Ubuntu]</ref> for {{Mac}} & {{Linux}}
* Is the port was opened for external users? [http://www.portchecktool.com/ Open Port Check Tool - Port Forwarding Port Check Tool]
* Is institutional/ISP firewall enabled? Contact your MIS. ([https://en.wikipedia.org/wiki/Management_information_system Management information system]) of your company or ISP?

other issue: 
* bandwidth cost too much by certain users
* exceed the request limit of (hardware) firewall
* the external connection of updated Windows was down until reboot {{Win}}
* Amazon EC2 security group
* refresh browser cache: [http://refreshyourcache.com/en/cache/ Refresh your cache - When hitting F5 just isn't enough!]

== Tools ==

# {{Gd}} [http://www.nirsoft.net/utils/cports.html CurrPorts: Monitoring TCP/IP network connections on Windows]
# [http://portforward.com/help/portcheck.htm PFPortCheck Program]: check TCP/UDP port from localhost(where you installed the program) to portforward.com
# [http://technet.microsoft.com/en-us/sysinternals/bb897437 TCPView for Windows]
# [http://check-host.net/ Check server: Check host - online website monitoring, Check IP] "checks the possibility of a TCP connection to host's specified port from different locations around the world." quoted from website. {{access | date=2015-08-02}}

== Related articles ==
* [https://errerrors.blogspot.com/2022/07/blog-post.html 怎樣排除網路連線逾時 (network connection timed out) 問題]

== References ==
<references />

{{Template:Troubleshooting}}

[[Category:Software]]
[[Category:Programming]]
[[Category:Web_Dev]]
[[Category:MySQL]]
[[Category:Linux]]
[[Category:Testing]]