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# Listen Fields

Changes in sing-box 1.12.0

netns
bind_interface
routing_mark
reuse_addr

Changes in sing-box 1.11.0

sniff
sniff_override_destination
sniff_timeout
domain_strategy
udp_disable_domain_unmapping

### Structure

    {
      "listen": "",
      "listen_port": 0,
      "bind_interface": "",
      "routing_mark": 0,
      "reuse_addr": false,
      "netns": "",
      "tcp_fast_open": false,
      "tcp_multi_path": false,
      "udp_fragment": false,
      "udp_timeout": "",
      "detour": "",

      // Deprecated

      "sniff": false,
      "sniff_override_destination": false,
      "sniff_timeout": "",
      "domain_strategy": "",
      "udp_disable_domain_unmapping": false
    }

### Fields

#### listen

Required

Listen address.

#### listen_port

Listen port.

#### bind_interface

Since sing-box 1.12.0

The network interface to bind to.

#### routing_mark

Since sing-box 1.12.0

Only supported on Linux.

Set netfilter routing mark.

Integers (e.g. `1234`) and string hexadecimals (e.g. `"0x1234"`) are supported.

#### reuse_addr

Since sing-box 1.12.0

Reuse listener address.

#### netns

Since sing-box 1.12.0

Only supported on Linux.

Set network namespace, name or path.

#### tcp_fast_open

Enable TCP Fast Open.

#### tcp_multi_path

Go 1.21 required.

Enable TCP Multi Path.

#### udp_fragment

Enable UDP fragmentation.

#### udp_timeout

UDP NAT expiration time.

`5m` will be used by default.

#### detour

If set, connections will be forwarded to the specified inbound.

Requires target inbound support, see Injectable.

#### sniff

Deprecated in sing-box 1.11.0

Inbound fields are deprecated and will be removed in sing-box 1.13.0, check Migration.

Enable sniffing.

See Protocol Sniff for details.

#### sniff_override_destination

Deprecated in sing-box 1.11.0

Inbound fields are deprecated and will be removed in sing-box 1.13.0.

Override the connection destination address with the sniffed domain.

If the domain name is invalid (like tor), this will not work.

#### sniff_timeout

Deprecated in sing-box 1.11.0

Inbound fields are deprecated and will be removed in sing-box 1.13.0, check Migration.

Timeout for sniffing.

`300ms` is used by default.

#### domain_strategy

Deprecated in sing-box 1.11.0

Inbound fields are deprecated and will be removed in sing-box 1.13.0, check Migration.

One of `prefer_ipv4` `prefer_ipv6` `ipv4_only` `ipv6_only`.

If set, the requested domain name will be resolved to IP before routing.

If `sniff_override_destination` is in effect, its value will be taken as a fallback.

#### udp_disable_domain_unmapping

Deprecated in sing-box 1.11.0

Inbound fields are deprecated and will be removed in sing-box 1.13.0, check Migration.

If enabled, for UDP proxy requests addressed to a domain, the original packet address will be sent in the response instead of the mapped domain.

This option is used for compatibility with clients that do not support receiving UDP packets with domain addresses, such as Surge.