Arguments to waitress.serveΒΆ

Here are the arguments you can pass to the waitress.serve` function or use in PasteDeploy configuration (interchangeably):


hostname or IP address (string) on which to listen, default, which means "all IP addresses on this host".


May not be used with listen


TCP port (integer) on which to listen, default 8080


May not be used with listen


New in version 1.0: Tell waitress to listen on combinations of host:port arguments. Combinations should be a quoted, space-delimited list, as in the following examples.

listen=" [::1]:8080"
listen="*:8080 *:6543"

A wildcard for the hostname is also supported and will bind to both IPv4/IPv6 depending on whether they are enabled or disabled.

IPv6 IP addresses are supported by surrounding the IP address with brackets.

Enable or disable IPv4 (boolean)
Enable or disable IPv6 (boolean)

Path of Unix socket (string), default is None. If a socket path is specified, a Unix domain socket is made instead of the usual inet domain socket.

Not available on Windows.

Octal permissions to use for the Unix domain socket (string), default is 600. Only used if unix_socket is not None.

New in version 1.1.1: A list of sockets. The sockets can be either Internet or UNIX sockets and have to be bound. Internet and UNIX sockets cannot be mixed. If the socket list is not empty, waitress creates one server for each socket. Default is [].


May not be used with listen, host, port or unix_socket

number of threads used to process application logic (integer), default 4
IP address of a client allowed to override url_scheme via the X_FORWARDED_PROTO header.
default wsgi.url_scheme value (string), default http; can be overridden per-request by the value of the X_FORWARDED_PROTO header, but only if the client address matches trusted_proxy.
server identity (string) used in "Server:" header in responses, default waitress
backlog is the value waitress passes to pass to socket.listen() (integer), default 1024. This is the maximum number of incoming TCP connections that will wait in an OS queue for an available channel. From listen(1): "If a connection request arrives when the queue is full, the client may receive an error with an indication of ECONNREFUSED or, if the underlying protocol supports retransmission, the request may be ignored so that a later reattempt at connection succeeds."
recv_bytes is the argument waitress passes to socket.recv() (integer), default 8192
send_bytes is the number of bytes to send to socket.send() (integer), default 18000. Multiples of 9000 should avoid partly-filled TCP packets, but don't set this larger than the TCP write buffer size. In Linux, /proc/sys/net/ipv4/tcp_wmem controls the minimum, default, and maximum sizes of TCP write buffers.
A tempfile should be created if the pending output is larger than outbuf_overflow, which is measured in bytes. The default is 1MB (1048576). This is conservative.
A tempfile should be created if the pending input is larger than inbuf_overflow, which is measured in bytes. The default is 512K (524288). This is conservative.
Stop creating new channels if too many are already active (integer). Default is 100. Each channel consumes at least one file descriptor, and, depending on the input and output body sizes, potentially up to three, plus whatever file descriptors your application logic happens to open. The default is conservative, but you may need to increase the number of file descriptors available to the Waitress process on most platforms in order to safely change it (see ulimit -a "open files" setting). Note that this doesn't control the maximum number of TCP connections that can be waiting for processing; the backlog argument controls that.
Minimum seconds between cleaning up inactive channels (integer), default 30. See "channel_timeout".
Maximum seconds to leave an inactive connection open (integer), default 120. "Inactive" is defined as "has received no data from a client and has sent no data to a client".
Boolean: turn off to not log premature client disconnect tracebacks. Default: True.
maximum number of bytes of all request headers combined (integer), 256K (262144) default)
maximum number of bytes in request body (integer), 1GB (1073741824) default.
Boolean: expose tracebacks of unhandled exceptions to client. Default: False.

New in version 0.8.3: The timeout value (seconds) passed to asyncore.loop to run the mainloop. Default: 1.


New in version 0.8.6: Boolean: switch from using select() to poll() in asyncore.loop. By default asyncore.loop() uses select() which has a limit of 1024 file descriptors. select() and poll() provide basically the same functionality, but poll() doesn't have the file descriptors limit. Default: False.

String: the value used as the WSGI SCRIPT_NAME value. Setting this to anything except the empty string will cause the WSGI SCRIPT_NAME value to be the value passed minus any trailing slashes you add, and it will cause the PATH_INFO of any request which is prefixed with this value to be stripped of the prefix. Default: the empty string.