MATLAB: Does “fopen” fail to connect to the “tcpip” server

clientconnectionerrorfopenInstrument Control Toolboxopenrefusedservertcpipunsuccessful

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This issue may occur if you have not opened a connection on a MATLAB with the server interface. This means, that on the machine where you run "tcpip" with "server" as the "NetworkRole", it is necessary to use "fopen" to open the connection. Make sure the server runs the following commands:

>> t = tcpip('0.0.0.0', 30000, 'NetworkRole', 'server');
>> fopen(t); % without this, there may be "Unsuccessful open: Connection refused: connect" error message

The server will be executing "fopen" and waiting for the client to connect. The server will finish executing "fopen" function the moment client connects using its own "fopen". If the server is not executing "fopen", then the client will not be able to connect.

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MATLAB: How to set a proxy server to use with the URLREAD and URLWRITE functions in MATLAB

In order to specify a proxy server for use in MATLAB, you will need to set two Java system properties: 'http.proxyHost' and 'http.proxyPort'. These properties correspond to the hostname of the proxy server, and the port that is used to connect to the proxy server, respectively.

If you are using MATLAB 7.0 (R14) or later versions, you can set these properties by going to "File -> Preferences -> Web". Then, check the "Use proxy to connect to the internet" checkbox and enter the values in the "Proxy server" and "Proxy port" editboxes.

If you are using a previous version of MATLAB, you will need to set these properties from the Command Window using the following commands:

java.lang.System.setProperty('http.proxyHost','myproxy.mycompany.com')
java.lang.System.setProperty('http.proxyPort','1234')

replacing 'myproxy' and '1234' with the appropriate values. You may want to add these commands to a startup.m file, so they are executed every time you start MATLAB. See the following for more information regarding startup.m:

http://www.mathworks.com/help/matlab/matlab_env/startup-options.html#brlkmbe-1

Alternately, use the following lines of code in your file:

com.mathworks.mlwidgets.html.HTMLPrefs.setUseProxy(true)
com.mathworks.mlwidgets.html.HTMLPrefs.setProxyHost('HostName')
com.mathworks.mlwidgets.html.HTMLPrefs.setProxyPort('1234')
%%the proxy authentication is required
com.mathworks.mlwidgets.html.HTMLPrefs.setUseProxyAuthentication(true)
com.mathworks.mlwidgets.html.HTMLPrefs.setProxyUsername('test')
com.mathworks.mlwidgets.html.HTMLPrefs.setProxyPassword('test')

If you are compiling and deploying your MATLAB code to a target machine, in order to set the same settings for your compiled application on the target machine, add the following lines to your MATLAB code before you compile:

if isdeployed
   com.mathworks.mlwidgets.html.HTMLPrefs.setUseProxy(true)
   com.mathworks.mlwidgets.html.HTMLPrefs.setProxyHost('HostName')
   com.mathworks.mlwidgets.html.HTMLPrefs.setProxyPort('Port')
end

where 'HostName' is the name of the Proxy Host and 'Port' is the port number on which the user needs to connect to the proxy server.

MATLAB: Might fopen fail on a tcpip object (127.0.0.1)

Several possibilities:

Your firewall / antivirus is blocking the connection
There is nothing listening on port 9300
the connection you're trying to establish is meant to be the server , in which case you need t = tcpip(tcpip('127.0.0.1', 9300, 'NetworkRole', 'server')
something else...

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Related Solutions

MATLAB: How to set a proxy server to use with the URLREAD and URLWRITE functions in MATLAB

MATLAB: Might fopen fail on a tcpip object (127.0.0.1)

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