Member Avatar for sDJh

Hello alltogether,

it's a really silly question actually, but I just can't figure it out. I want to write a simple server, that serves the HTTP-protocoll (Port 80). The connection does work, when I let the programme run on port 8080, but Mac OS prohibits the connection on port 80. What can I do?

Many, many thanks
Simon

PS I thought I posted this thread yesterday already, but can't find it anymore. So if the old thread still exist, please delte this one.

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  • Latest Post Latest Post by John A

Dani AI

Generated

As noted, your server already works on 8080 and pointed toward the system-level restriction you hit. Here are practical, safe ways to get HTTP on port 80 without guessing which macOS version you have — pick the one that fits your setup.

One-line port-forward (no need to run your app as root)

# forward external interface en0 -> local server 127.0.0.1:8080
echo "rdr pass on en0 inet proto tcp from any to any port 80 -> 127.0.0.1 port 8080" | sudo pfctl -f -
sudo pfctl -e

# to stop pf rules:
sudo pfctl -d

Use lo0 instead of en0 if you only need localhost redirection (127.0.0.1). Make the rule persistent by adding it to /etc/pf.conf or an anchor.

Run as a proper daemon via launchd (safe for production)

# save as /Library/LaunchDaemons/com.example.myserver.plist (owner root:wheel, chmod 644)
<?xml version="1.0" encoding="UTF-8"?>
<plist version="1.0">
<dict>
  <key>Label</key><string>com.example.myserver</string>
  <key>ProgramArguments</key>
  <array><string>/usr/local/bin/myserver</string></array>
  <key>RunAtLoad</key><true/>
  <key>UserName</key><string>root</string>
  <key>KeepAlive</key><true/>
  <key>StandardOutPath</key><string>/var/log/myserver.out</string>
  <key>StandardErrorPath</key><string>/var/log/myserver.err</string>
</dict>
</plist>

# load it
sudo launchctl load -w /Library/LaunchDaemons/com.example.myserver.plist

This lets launchd start the binary with root privileges so it can bind port 80; drop privileges inside the process after binding if possible.

Reverse-proxy (recommended if you want unprivileged app)

# nginx example: listen on 80 and proxy to 8080
server {
    listen 80;
    server_name _;
    location / { proxy_pass http://127.0.0.1:8080; }
}

Run nginx/Apache (they handle low ports safely) and proxy traffic to your app on 8080.

Quick troubleshooting and safety notes

  • Check macOS firewall settings in System Preferences > Security & Privacy > Firewall; app-level blocking can interfere.
  • Inspect pf rules with sudo pfctl -sr and check logs if connections are dropped.
  • Avoid running app as root long-term; bind first, then drop privileges (setuid) or use a proxy.
  • Behavior and tools (launchctl, pf) evolved across macOS releases — verify commands on your OS if something fails.
Member Avatar for John A

Most likely you weren't running the program as a privileged user. Mac OS X requires administrative privileges to bind on ports < 1024.

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