Why Am I Getting the 'Error: listen EADDRINUSE' When Running a Node.JS Server?

Fixing Error: EADDRINUSE while Using Node.JS

Issue Overview:

When attempting to run a server on port 80 while performing a request using XMLHttpRequest, the error "Error: listen EADDRINUSE" may occur in Node.JS. This error indicates that the server is unable to bind to the specified port because another process is already using it.

Why it's a Problem:

Node.JS requires exclusive use of the port it binds to, preventing requests from being made while the server is running. Browsers can connect to the server and make requests because they use ephemeral ports.

Server Implementation:

net.createServer(function (socket) {
    socket.name = socket.remoteAddress + ":" + socket.remotePort;
    console.log('connection request from: ' + socket.remoteAddress);
    socket.destroy();
  }).listen(options.port);

Request Code:

var xhr = new XMLHttpRequest();

xhr.onreadystatechange = function() {
    sys.puts("State: " + this.readyState);

    if (this.readyState == 4) {
        sys.puts("Complete.\nBody length: " + this.responseText.length);
        sys.puts("Body:\n" + this.responseText);
    }
};

xhr.open("GET", "http://mywebsite.com");
xhr.send();

Solution:

To resolve this issue, it is necessary to ensure that no other process is binding to port 80. This can be achieved by killing the offending process using the following command:

killall -9 node

Caution: This command will terminate all running Node.JS processes, so use it with caution.

Verifying Termination:

To verify that the process has been terminated, run the following command:

ps ax

If no Node.JS processes are listed, the issue should be resolved.

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