SYSTEMD-SOCKET-PROXYD(8)                 SYSTEMD-SOCKET-PROXYD(8)

     NAME
          systemd-socket-proxyd - Bidirectionally proxy local sockets
          to another (possibly remote) socket

     SYNOPSIS
          systemd-socket-proxyd [OPTIONS...] HOST:PORT

          systemd-socket-proxyd [OPTIONS...] UNIX-DOMAIN-SOCKET-PATH

     DESCRIPTION
          systemd-socket-proxyd is a generic socket-activated network
          socket forwarder proxy daemon for IPv4, IPv6 and UNIX stream
          sockets. It may be used to bi-directionally forward traffic
          from a local listening socket to a local or remote
          destination socket.

          One use of this tool is to provide socket activation support
          for services that do not natively support socket activation.
          On behalf of the service to activate, the proxy inherits the
          socket from systemd, accepts each client connection, opens a
          connection to a configured server for each client, and then
          bidirectionally forwards data between the two.

          This utility's behavior is similar to socat(1). The main
          differences for systemd-socket-proxyd are support for socket
          activation with "Accept=no" and an event-driven design that
          scales better with the number of connections.

     OPTIONS
          The following options are understood:

          -h, --help
              Print a short help text and exit.

          --version
              Print a short version string and exit.

          --connections-max=, -c
              Sets the maximum number of simultaneous connections,
              defaults to 256. If the limit of concurrent connections
              is reached further connections will be refused.

          --exit-idle-time=
              Sets the time before exiting when there are no
              connections, defaults to infinity. Takes a unit-less
              value in seconds, or a time span value such as "5min
              20s".

     EXIT STATUS
          On success, 0 is returned, a non-zero failure code

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          otherwise.

     EXAMPLES
        Simple Example
          Use two services with a dependency and no namespace
          isolation.

          Example 1. proxy-to-nginx.socket

              [Socket]
              ListenStream=80

              [Install]
              WantedBy=sockets.target

          Example 2. proxy-to-nginx.service

              [Unit]
              Requires=nginx.service
              After=nginx.service
              Requires=proxy-to-nginx.socket
              After=proxy-to-nginx.socket

              [Service]
              ExecStart=/lib/systemd/systemd-socket-proxyd /run/nginx/socket
              PrivateTmp=yes
              PrivateNetwork=yes

          Example 3. nginx.conf

              [...]
              server {
                  listen       unix:/run/nginx/socket;
                  [...]

          Example 4. Enabling the proxy

              # systemctl enable --now proxy-to-nginx.socket
              $ curl http://localhost:80/

          If nginx.service has StopWhenUnneeded= set, then passing
          --exit-idle-time= to systemd-socket-proxyd allows both
          services to stop during idle periods.

        Namespace Example
          Similar as above, but runs the socket proxy and the main
          service in the same private namespace, assuming that
          nginx.service has PrivateTmp= and PrivateNetwork= set, too.

          Example 5. proxy-to-nginx.socket

              [Socket]

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              ListenStream=80

              [Install]
              WantedBy=sockets.target

          Example 6. proxy-to-nginx.service

              [Unit]
              Requires=nginx.service
              After=nginx.service
              Requires=proxy-to-nginx.socket
              After=proxy-to-nginx.socket
              JoinsNamespaceOf=nginx.service

              [Service]
              ExecStart=/lib/systemd/systemd-socket-proxyd 127.0.0.1:8080
              PrivateTmp=yes
              PrivateNetwork=yes

          Example 7. nginx.conf

              [...]
              server {
                  listen       8080;
                  [...]

          Example 8. Enabling the proxy

              # systemctl enable --now proxy-to-nginx.socket
              $ curl http://localhost:80/

     SEE ALSO
          systemd(1), systemd.socket(5), systemd.service(5),
          systemctl(1), socat(1), nginx(1), curl(1)

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