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タイトル
Checking for blocked ports from a remote computer when TELNET is not available -
説明
Blocked ports often contribute to product connection issues.Typically, Support requests to use TELNET or even run a “portable” version of PuTTY to test the connection.- Increasingly customers are reluctant to install Telnet on their servers for security reasons.
In lieu of using Telnet, a browser or a Linux command line utility can be an alternative for port testing. -
対策
Using a browser
Google Chrome
Port blocked “refused to connect” or is not listening
Port is open (but is rejected for various reasons because it is not a web browser port)
Internet Explorer
Port blocked or not listening
Port open but rejected
Mozilla Firefox
Port blocked or not listening
Port Open
In LINUX From the command line
Using Netcat with CentOS
Output a new blank command line or message “connection reset by peer” if the port is open; Output “Connection refused” if the port is closed.
Port is open
[root@foglight /]# nc 192.168.1.48 8080 < /dev/null
[root@foglight /]#[root@foglight /]# nc 192.168.1.48 135 < /dev/null
[root@foglight /]#[root@foglight /]# nc 192.168.1.50 1433 < /dev/null
[root@foglight /]#[root@foglight /]# nc 192.168.1.48 5029 < /dev/null
Ncat: Connection reset by peer.[root@foglight /]# nc 192.168.1.41 1521 < /dev/null
[root@foglight /]#“Connection refused” if the port is closed.
[root@foglight /]# nc 192.168.1.48 8081 < /dev/null
Ncat: Connection refused.Using Netcat with Oracle Linux or RHEL
Port is open
[root@Foglight2 orauser]# nc -vz 192.168.1.215 8080 < /dev/null
Connection to 192.168.1.215 8080 port [tcp/webcache] succeeded![root@Foglight2 orauser]# nc -vz 192.168.1.215 135 < /dev/null
Connection to 192.168.1.215 135 port [tcp/epmap] succeeded![root@Foglight2 orauser]# nc -vz 192.168.1.218 1433 < /dev/nullConnection to 192.168.1.218 1433 port [tcp/ms-sql-s] succeeded![root@Foglight2 orauser]# nc -vz 192.168.1.215 5029 < /dev/nullConnection to 192.168.1.215 5029 port [tcp/infobright] succeeded![root@Foglight2 orauser]# nc -vz 192.168.1.216 1521 < /dev/null
Connection to 192.168.1.216 1521 port [tcp/ncube-lm] succeeded!“Connection refused” if the port is closed.[root@Foglight2 orauser]# nc -vz 192.168.1.215 8081 < /dev/nullnc: connect to 192.168.1.215 port 8081 (tcp) failed: Connection refusedUsing Curl (with CentOS)
Construct an HTTP URI from the hostname and port as the first argument to curl. If curl can connect, it will report a protocol mismatch and exit (if the listener isn't a web service). If curlcannot connect, it will time out.
This is a blocked port either closed or blocked by a firewall
[root@foglight /]# curl 192.168.1.48:8081
curl: (7) Failed connect to 192.168.1.48:8081; Connection refused
For example a PI repository is running on this remote server
[root@foglight /]# curl 192.168.1.48:5029
curl: (56) Recv failure: Connection reset by peer
This is an open FMS webpage, there is no error and a new command line entry is displayed
[root@foglight /]# curl 192.168.1.48:8080
[root@foglight /]#
This is open Windows RPC port, this will establish a connection. Use Ctrl-C to end the connection
[root@foglight /]# curl 192.168.1.48:135
^C
[root@foglight /]#
This is an open SQL Server port
[root@foglight /]# curl 192.168.1.50:1433
curl: (52) Empty reply from server
This is an open Oracle port
[root@foglight /]# curl 192.168.1.41:1521
curl: (52) Empty reply from server
Using Echo (this must be done on the remote host)
This is an open local port
[root@foglight /]# echo > /dev/tcp/localhost/80 && echo Port Open || echo Port closed
-bash: connect: Connection refused
-bash: /dev/tcp/localhost/80: Connection refused
Port closedThis is a closed local port
[root@foglight /]# echo > /dev/tcp/localhost/22 && echo Port Open || echo Port closed
Port Open
On Windows (newer OS versions with Powershell 4.0 and higher)
To check the Powershell version, run Get-Host
PS C:\Users\foglight> Get-Host
Name : ConsoleHost
Version : 5.1.16299.98
InstanceId : 011f9552-8ce6-46a6-a7a6-8e61c7e37b46
UI : System.Management.Automation.Internal.Host.InternalHostUserInterface
CurrentCulture : en-US
PrivateData : Microsoft.PowerShell.ConsoleHost+ConsoleColorProxy
DebuggerEnabled : True
IsRunspacePushed : False
Runspace : System.Management.Automation.Runspaces.LocalRunspaceThen run the connection test using Test-NetConnection
This is an open port
PS C:\users\foglight> test-netconnection -computername 192.168.1.48 -port 8080ComputerName : 192.168.1.48RemoteAddress : 192.168.1.48RemotePort : 8080InterfaceAlias : EthernetSourceAddress : 192.168.1.51TcpTestSucceeded : True
This is a closed port
PS C:\WINDOWS\system32> test-netconnection -computername 192.168.1.48 -port 8081
WARNING: TCP connect to (192.168.1.48 : 8081) failedComputerName : 192.168.1.48RemoteAddress : 192.168.1.48RemotePort : 8081InterfaceAlias : EthernetSourceAddress : 192.168.1.51PingSucceeded : TruePingReplyDetails (RTT) : 198 msTcpTestSucceeded : False