Set MATLAB Web App Server Port number to below 1024 on Linux

I want to use port 80 for my web app server on Linux. But web app cannot start. It reports below error in the log file

00000014 2023-05-18 12:15:08 0x00007faf377fe700 agent::spf::legacyservicepublisher V Exception caught: Dynamic exception type: foundation::http::TCPConfigurationError

std::exception::what: Failed to open server socket on 0.0.0.0, for given port range: [80,80]

I am pretty sure port 80 is not being used by other service.

Answer 1

[MathWorks Support Team]

By default, ip_unprivileged_port_start is set to 1024 in Linux. It defines the first unprivileged port in the network namespace. Privileged ports require root or CAP_NET_BIND_SERVICE in order to bind to them. This is why you cannot set web app server to use port 80, or any value below 1024 if you have default ip_unprivileged_port_start value.

To workaround this:

Use port forwarding with command "sudo iptables -t nat -A PREROUTING -p tcp --dport $external_port -j REDIRECT --to-ports $server_site_port". For example your web app server is set to port 9988 and you want to access it with port 80 in the url. The command is "sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 9988"

Alternatively, you can allow listening on all privileged ports using this commands "sudo sysctl net.ipv4.ip_unprivileged_port_start=0".