Configuration reference

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Server & network

server_portdefault: 1511

Description	This specifies the port number the hub should listen on.
Type	number (1–65535)
Default	`1511`
Since	uhub 0.1.0

server_bind_addrdefault: "any"

Description	Specify the IP address the local hub should bind to. This can be an IPv4 or IPv6 address, or one of the special addresses "any" or "loopback". When "any" or "loopback" is used, the hub will automatically detect if IPv6 is supported and prefer that.
Type	String
Default	`"any"`
Since	uhub 0.1.2
Syntax	IPv4 address, IPv6 address, "any" or "loopback"
Example	To listen to a specific IP: server_bind_addr = "192.168.12.69" To listen to any IPv4 address: server_bind_addr = "0.0.0.0" Or to listen to any address including IPv6 (if supported): server_bind_addr = "any"

server_listen_backlogdefault: 50

Description	This specifies the number of connections the hub will be able to accept in the backlog before they must be processed by the hub. A too low number here will mean the hub will not accept connections fast enough when users are reconnecting really fast. The hub should under normal circumstances be able to empty the listen backlog several times per second.
Type	number ≥ 5
Default	`50`
Since	uhub 0.3.0

server_alt_portsdefault: ""

Description	In addition to the server_port the hub can listen to a list of alternative ports.
Type	String
Default	`""`
Since	uhub 0.3.0
Example	`server_alt_ports = 1295,1512,53990`

server_reuseportdefault: no

Description	Set SO_REUSEPORT on the listening socket so that multiple hub processes can bind the same server_port; the kernel then load-balances incoming client connections across them. This is the basis for running one logical hub as several worker processes on a multi-core machine (linked together so they share one roster and SID space). Enabled automatically when "workers" is greater than 1. Only set it by hand if you supervise the worker processes yourself (e.g. a systemd template).
Type	boolean
Default	`no`
Since	uhub 0.7.0

keepalive_intervaldefault: 120

Description	How long a logged-in connection may go without the hub writing anything to it before the hub sends an empty line (`\n`) as a keepalive. Clients ignore empty lines, so this is only there to make the hub write: a write to a connection the peer has already forgotten (a NAT or firewall dropped the state, or the client went away without a FIN) fails or is reset, and the hub reaps the stale user. This matters because clients do the same thing in the other direction. A client whose keepalive is reset reconnects immediately, and if the hub is still holding the dead connection the new login is rejected as "CID taken". Poking idle connections closes that window. The same value doubles as how long a session must have been silent before a login presenting the same CID may take its place: a live client is expected to be heard from at least that often, so a session that is still talking is never displaced, while one that has gone quiet gives way to its owner reconnecting. A different CID never displaces anything that is still alive. If this is 0 the keepalive is disabled and stale connections are only detected by TCP keepalive, which takes several minutes. Connections that already have data queued are skipped: they have a pending write of their own, and adding to the backlog would not tell the hub anything new.
Type	number (0–3600)
Default	`120`
Since	uhub 0.8.0
Syntax	0 = off
Example	To poke idle connections every minute: keepalive_interval = 60

nat_overridedefault: ""

Description	Clients connecting from one of these IP ranges (typically the hub's own LAN, or a NAT gateway) are permitted to advertise the IPv4 address they claim in their INF instead of the (often private) address the hub observes. This lets a client behind NAT be reachable by remote peers for connection setup and transfers. Only list networks you trust. Ranges may be given as CIDR, as a lo-hi range, or as a single address. This replaces the former nat_ip entries in the acl file (file_acl).
Type	String
Default	`""`
Since	uhub 0.8.0
Example	`nat_override = 10.0.0.0/8,192.168.0.0/16`

Hub options

hub_enableddefault: yes

Description	Use this to disable the hub for a while.
Type	boolean
Default	`yes`
Since	uhub 0.1.3

show_bannerdefault: yes

Description	If enabled, the hub will announce the software version running to clients when they connect with a message like: "Powered by uhub/0.x.y"
Type	boolean
Default	`yes`
Since	uhub 0.1.0

show_banner_sys_infodefault: yes

Description	If enabled, the hub will announce the operating system and CPU architecture to clients when they join. This option has no effect if show_banner is disabled.
Type	boolean
Default	`yes`
Since	uhub 0.3.0

max_usersdefault: 500

Description	The maximum amount of users allowed on the hub. No new users will be allowed to enter the hub if this number is exceeded, however privileged users (operators, admins, etc) are still able to log in.
Type	number (1–1048576)
Default	`500`
Since	uhub 0.1.0
Example	To run a hub for max 25 users: max_users = 25

registered_users_onlydefault: no

Description	If this is enabled only registered users will be able to use the hub. Users are registered through an authentication plugin (for example mod_auth_sqlite or mod_auth_simple), configured via file_plugins.
Type	boolean
Default	`no`
Since	uhub 0.1.1

register_selfdefault: no

Description	If this is enabled guests can register their nickname on the hub using !register command. Otherwise only operators can register users.
Type	boolean
Default	`no`
Since	uhub 0.4.0

obsolete_clientsdefault: no

Description	If this is enabled users using old ADC clients are allowed to enter the hub, however they cannot log in using passwords since the protocols are incompatible.
Type	boolean
Default	`no`
Since	uhub 0.3.1

chat_is_privilegeddefault: no

Description	If enabled only operators and admins are allowed to chat in the main chat.
Type	boolean
Default	`no`
Since	uhub 0.2.4

chat_rich_textdefault: yes

Description	When enabled the hub advertises the `RTF0` extension, which lets clients mark a chat message as rich text formatted with the `RT1` flag. Rich text messages may embed images by URL, using the form `![description](url)`, so clients that support the extension will fetch and display remote images posted in chat. Disable this on hubs where that is unwanted: the hub then stops advertising `RTF0` and removes the `RT` flag from every relayed message, so no client renders posted images. Clients that do not support `RTF0` never receive the `RT` flag and see the plain message text either way.
Type	boolean
Default	`yes`
Since	uhub 0.8.0

hub_namedefault: "uhub"

Description	Configures the name of the hub
Type	String
Default	`"uhub"`
Since	uhub 0.1.0
Example	`hub_name = "my hub"`

hub_descriptiondefault: "no description"

Description	This is the description of the hub, as seen by users and hub lists.
Type	String
Default	`"no description"`
Since	uhub 0.1.0
Example	`hub_description = "a friendly hub for friendly people"`

redirect_addrdefault: ""

Description	This is the redirect address used when the hub wants to redirect a client for not fulfilling some requirements.
Type	String
Default	`""`
Since	uhub 0.3.2

low_bandwidth_modedefault: no

Description	If this is enabled the hub will remove excessive information from each user's info message before broadcasting to all connected users. Description, e-mail address will be removed. This saves upload bandwidth for the hub.
Type	boolean
Default	`no`
Since	uhub 0.2.2

Hub information

hub_addressdefault: ""

Description	The DNS name or IP address clients use to reach this hub. Sent to clients that support the ADC PING extension and to a registration server (the "HH" field). It is normalized to a complete adc:// or adcs:// URL with a port: a missing scheme (adcs:// when tls_enable is set, otherwise adc://) and a missing port (server_port) are filled in automatically, so a bare host is accepted. Leave empty to omit.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`hub_address = "adc://hub.example.com:1511" A bare host such as "hub.example.com" is expanded to adc(s)://hub.example.com:<server_port>.`

hub_websitedefault: ""

Description	The hub's website. Sent to clients that support the ADC PING extension (the "WS" field). Leave empty to omit.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`hub_website = "https://www.example.com"`

hub_networkdefault: ""

Description	The name of the network this hub belongs to. Sent to clients that support the ADC PING extension (the "NE" field). Leave empty to omit.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`hub_network = "Example Network"`

hub_ownerdefault: ""

Description	The name of the hub owner. Sent to clients that support the ADC PING extension (the "OW" field). Leave empty to omit.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`hub_owner = "Jane Doe"`

reg_server_urldefault: ""

Description	The HTTP/HTTPS URL of an ADC hub-list registration server. When set, the hub sends a single POST request to this URL at startup with its own IINF line as the body, expecting a "202 Accepted" reply, so hub lists can pick the hub up automatically. Leave empty (the default) to disable; this is the on/off switch, so leave it empty for private hubs. The path defaults to /register and the port defaults to 80 (http) or 443 (https). For the announce to carry a usable address, also configure hub_address (the HH field): it is normalized to an adc:// or adcs:// URL including the port, so a missing scheme (adcs:// when tls_enable is set, otherwise adc://) and a missing port (server_port) are filled in automatically. No retries are attempted; the outcome is logged.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`reg_server_url = "http://adcreg.dchublist.org:8080/register"`

Limits

max_connections_per_ipdefault: 0

Description	Limits how many connections a single IP address may hold at once, counting both connections still in the pre-login (probe) phase and logged-in users. This bounds connection-slot exhaustion from a single source (a flood of connections that never complete login, or are churned to keep every slot occupied). If this is 0 the limit is disabled. Note that clients sharing one public IP (behind NAT) all count against the same limit, so pick a value that accommodates your largest expected shared address.
Type	number (0–1048576)
Default	`0`
Since	uhub 0.7.1
Syntax	0 = off
Example	To allow at most 10 concurrent connections per IP: max_connections_per_ip = 10

limit_max_hubs_userdefault: 10

Description	This limits the number of hubs a user can be logged into as a guest user. If this number is exceeded, the user will not be allowed to enter the hub.
Type	number ≥ 0
Default	`10`
Since	uhub 0.2.0
Syntax	0 = off

limit_max_hubs_regdefault: 10

Description	This limits the number of hubs a user can be logged into as a registered user. If this number is exceeded, the user will not be allowed to enter the hub.
Type	number ≥ 0
Default	`10`
Since	uhub 0.2.0
Syntax	0 = off

limit_max_hubs_opdefault: 10

Description	This limits the number of hubs a user can be logged into as an operator. If this number is exceeded, the user will not be allowed to enter the hub.
Type	number ≥ 0
Default	`10`
Since	uhub 0.2.0
Syntax	0 = off

limit_max_hubsdefault: 25

Description	Limit the number of hubs a user can be logged into in total regardless of registrations or privileges. If this number is exceeded, the user will not be allowed to enter the hub.
Type	number ≥ 0
Default	`25`
Since	uhub 0.2.0
Syntax	0 = off

limit_min_hubs_userdefault: 0

Description	Only allow users that are logged into other hubs with guest privileges to enter this hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off

limit_min_hubs_regdefault: 0

Description	Only allow users that are logged into other hubs as a registered user to enter this hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off

limit_min_hubs_opdefault: 0

Description	Only allow users that are logged into other hubs with operator privileges to enter this hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off

limit_min_sharedefault: 0

Description	Minimum share limit in megabytes (MiB). Users sharing less than this will not be allowed to enter the hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off
Example	To require users to share at least 1 GB in order to enter the hub: limit_min_share = 1024

limit_max_sharedefault: 0

Description	Maximum share limit in megabytes (MiB). Users sharing more than this will not be allowed to enter the hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off

limit_min_slotsdefault: 0

Description	Minimum number of upload slots required. Users with less than this will not be allowed to enter the hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off

limit_max_slotsdefault: 0

Description	Maximum number of upload slots allowed. Users with more than this will not be allowed to enter the hub.
Type	number ≥ 0
Default	`0`
Since	uhub 0.2.0
Syntax	0 = off

limit_min_searchdefault: 0

Description	Minimum length (in bytes) of a substring search term. Searches whose longest include term ("AN") is shorter than this are rejected. Very short terms (such as a single letter) match a huge number of files and generate a lot of traffic through the hub, so requiring a few characters keeps searches precise and reduces load. Exact content (TTH) searches and searches from operators and above are never restricted.
Type	number (0–255)
Default	`0`
Since	uhub 0.7.0
Syntax	0 = off
Example	To require search terms to be at least 3 characters long: limit_min_search = 3

Flood control

flood_ctl_intervaldefault: 0

Description	This is the time interval that will be used for all flood control calculations. If this is 0 then all flood control is disabled.
Type	number (1–60)
Default	`0`
Since	uhub 0.3.1
Syntax	0 = off
Example	To limit maximum chat messages to 5 messages on 10 seconds: flood_ctl_interval = 10 flood_ctl_chat = 5

flood_ctl_chatdefault: 0

Description	If this is 0 then no flood control is disabled for chat messages.
Type	number
Default	`0`
Since	uhub 0.3.1
Syntax	0 = off

flood_ctl_connectdefault: 0

Description	If this is 0 then no flood control is disabled for connection requests.
Type	number
Default	`0`
Since	uhub 0.3.1
Syntax	0 = off

flood_ctl_searchdefault: 0

Description	If this is 0 then no flood control is disabled for search requests.
Type	number
Default	`0`
Since	uhub 0.3.1
Syntax	0 = off

flood_ctl_updatedefault: 0

Description	If this is 0 then no flood control is disabled for info updates (INF messages).
Type	number
Default	`0`
Since	uhub 0.3.1
Syntax	0 = off

flood_ctl_extrasdefault: 0

Description	Extra messages are messages that don't fit into the category of chat, search, update or connect.
Type	number
Default	`0`
Since	uhub 0.3.1
Syntax	0 = off

TLS

tls_enabledefault: no

Description	Enables/disables TLS/SSL support. tls_certificate and tls_private_key must be set if this is enabled.
Type	boolean
Default	`no`
Since	uhub 0.3.0

tls_requiredefault: no

Description	If TLS/SSL support is enabled it can either be optional or mandatory. If this option is disabled then SSL/TLS is not required to enter the hub, however it is possible to enter either with or without. This option has no effect unless tls_enable is enabled.
Type	boolean
Default	`no`
Since	uhub 0.3.0

tls_require_redirect_addrdefault: ""

Description	This is the redirect address used when the hub wants to redirect a client for not using ADCS. For instance a hub at adc://adc.example.com might redirect to adcs://adc.example.com
Type	String
Default	`""`
Since	uhub 0.3.3

tls_certificatedefault: ""

Description	Path to a TLS/SSL certificate or certificate chain (PEM format).
Type	file
Default	`""`
Since	uhub 0.3.0

tls_private_keydefault: ""

Description	Path to a TLS/SSL private key (PEM format).
Type	file
Default	`""`
Since	uhub 0.3.0

tls_ciphersuitedefault: "ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS"

Description	This is a colon separated list of preferred ciphers in the OpenSSL format. It only affects TLS 1.2 and earlier; the TLS 1.3 cipher suites are configured separately with `tls_ciphersuites`.
Type	String
Default	`"ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS"`
Since	uhub 0.5.0
Example	High security with emphasis on forward secrecy: tls_ciphersuite = "ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS" Allow ChaCha20/Poly1305 which are secure, yet generally faster: tls_ciphersuite = "ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA"

tls_ciphersuitesdefault: "TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"

Description	This is a colon separated list of preferred TLS 1.3 cipher suites in the OpenSSL format. TLS 1.3 uses a separate, fixed set of cipher suites that are named differently from earlier versions, so they cannot be mixed with `tls_ciphersuite`. The default enables all standard TLS 1.3 suites. This setting has no effect unless TLS 1.3 is negotiated.
Type	String
Default	`"TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"`
Since	uhub 0.6.0
Example	Prefer AES-256-GCM, then ChaCha20/Poly1305, then AES-128-GCM: tls_ciphersuites = "TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"

tls_versiondefault: "1.2"

Description	This allows you to specify the minimum TLS version the hub requires from connecting clients in order to connect to the hub. Valid values are "1.2" and "1.3". TLS version 1.2 is recommended and enabled by default. TLS version 1.3 can be required to admit only the most modern clients. TLS versions below 1.2 are deprecated and no longer supported.
Type	String
Default	`"1.2"`
Since	uhub 0.5.0

Metrics

metrics_enabledefault: no

Description	When enabled, the hub answers HTTP `GET` requests for the metrics path (see `metrics_path`) on the regular server port(s) with a Prometheus text-exposition document. A valid bearer token (`metrics_token`) is required; if no token is configured the endpoint stays disabled. The endpoint is served on the same port(s) as ADC, both over plain HTTP and, when `tls_enable` is set, over HTTPS (scrape with `https://`). Use HTTPS to keep the bearer token confidential: plain HTTP is also accepted on the same port, so over plain HTTP the token is exposed on an untrusted network -- scrape over loopback/a trusted network, or use HTTPS.
Type	boolean
Default	`no`
Since	uhub 0.7.0

metrics_tokendefault: ""

Description	The token that scrapers must present in an `Authorization: Bearer <token>` request header. The metrics endpoint is refused unless this is set to a non-empty value.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`metrics_token = "a-long-random-secret"`

metrics_pathdefault: "/metrics"

Description	The HTTP path that returns metrics. Requests for any other path receive 404. Change this to obscure the endpoint if desired. Must begin with a slash.
Type	String
Default	`"/metrics"`
Since	uhub 0.7.0

Federation & scaling

workersdefault: 1

Description	Number of worker processes to run as a single logical hub on a multi-core machine. With workers greater than 1, the hub forks that many processes that share the client port (SO_REUSEPORT, so the kernel spreads connections across cores) and link to each other over Unix sockets, presenting one unified roster and SID space to clients. Each worker is a normal single-threaded hub, so this scales the CPU-bound work (especially TLS) across cores without any threading. 1 (the default) runs a single process. 0 means auto: one worker per online CPU. The master process only supervises the workers (restarting any that exit); it serves no clients itself.
Type	number (0–256)
Default	`1`
Since	uhub 0.7.0

worker_socket_dirdefault: "/tmp"

Description	Directory in which the master creates the Unix domain sockets that worker processes use to link to each other (one per worker). Must be a short path (the socket path is limited to about 108 bytes) on a local filesystem, and should be private to the hub user. Only used when workers is greater than 1.
Type	String
Default	`"/tmp"`
Since	uhub 0.7.0

dns_thread_pool_sizedefault: 4

Description	Hostname resolution (for hub linking and registration server announcements) runs on a pool of background threads so the main event loop never blocks on a slow DNS lookup. This option sets the number of worker threads in that pool. A small pool is plenty for a typical hub; raise it only if a large number of outbound lookups must run concurrently. Changing this value takes effect on restart, not on a configuration reload.
Type	number (1–64)
Default	`4`
Since	uhub 0.7.0

link_peerdefault: ""

Description	Address (host:port) of an upstream hub to establish a persistent link to. Empty disables outbound linking.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`link_peer = hub2.example.org:1512`

link_secretdefault: ""

Description	Shared secret that both ends of a link must hold. Links authenticate by proving knowledge of this secret via a nonce challenge-response; the secret itself is never sent over the wire.
Type	String
Default	`""`
Since	uhub 0.7.0

auth_proxydefault: no

Description	Master-slave authentication for linked hubs. When enabled this node is an auth slave: it holds no user accounts of its own and defers registered-user login to its upstream linked hub (the master), which keeps the only copy of the account database. The slave asks the master whether a nick is registered, and forwards the password challenge-response to the master to verify, so passwords never leave the master. Leave disabled on the master (the hub that loads the auth plugin with the accounts). Guests are unaffected and log in locally.
Type	boolean
Default	`no`
Since	uhub 0.7.0

link_socketdefault: ""

Description	Path to a Unix domain socket this hub listens on for inbound links from other hub processes on the same machine. Used to link worker processes of one logical hub without routing link traffic through the shared client port. Empty disables the Unix-socket listener (TCP links on the normal port still work). A link_peer that begins with "/" connects to such a socket. Protect the socket with filesystem permissions; it grants the same privileges as any link.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`link_socket = /run/uhub/worker-0.sock`

node_countdefault: 1

Description	Total number of nodes in a linked cluster. The ~1M ADC SID space is split into this many disjoint windows so each node allocates globally-unique SIDs without coordination. 1 = stand-alone.
Type	number (1–1048576)
Default	`1`
Since	uhub 0.7.0

node_iddefault: 0

Description	Zero-based index of this hub within the cluster; must be unique per node and less than node_count. Selects which SID window this node allocates from. Ignored when node_count is 1. Set to -1 to lease a SID window dynamically from the cluster over the link instead of configuring a fixed index (the node defers local logins until the lease is granted).
Type	number (-1–1048575)
Default	`0`
Since	uhub 0.7.0

hbri_enabledefault: no

Description	When enabled, the hub advertises the HBRI extension and lets dual-stack clients prove reachability on both IPv4 and IPv6. After a client logs in over one protocol, the hub asks it to open a short-lived secondary connection over the other protocol; on success the client's INF will carry both an IPv4 (I4) and an IPv6 (I6) address, so users behind either protocol can connect to each other. This requires the hub to be reachable on both IPv4 and IPv6 and both hbri_address4 and hbri_address6 to be configured. If either is empty, HBRI is not advertised.
Type	boolean
Default	`no`
Since	uhub 0.7.0

hbri_address4default: ""

Description	The public IPv4 address clients should connect to for HBRI secondary-protocol validation. Must be an address the hub actually listens on (it shares server_port). Leave empty to disable HBRI.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`hbri_address4 = "192.0.2.10"`

hbri_address6default: ""

Description	The public IPv6 address clients should connect to for HBRI secondary-protocol validation. Must be an address the hub actually listens on (it shares server_port). Leave empty to disable HBRI.
Type	String
Default	`""`
Since	uhub 0.7.0
Example	`hbri_address6 = "2001:db8::10"`

Files & buffers

max_recv_bufferdefault: 4096

Description	Maximum receive buffer allowed before commands are processed. If a single ADC message exceeds this limit, it will be discarded by the hub. Capped at MAX_RECV_BUF (65535), the size of the per-thread receive buffer the hub reads into.
Type	number (1024–65535)
Default	`4096`
Since	uhub 0.1.3

max_send_bufferdefault: 131072

Description	Maximum amount of bytes allowed to be queued for sending to any particular user before the hub will disconnect the user. The lower the limit, the more aggressive the hub will be to disconnect slow clients. Use with caution.
Type	number ≥ 2048
Default	`131072`
Since	uhub 0.1.3

max_send_buffer_softdefault: 98304

Description	Same as max_send_buffer, however low priority messages may be discarded if this limit is reached. Use with caution.
Type	number ≥ 1024
Default	`98304`
Since	uhub 0.1.3

max_chat_historydefault: 20

Description	This specifies the number of main chat messages that are kept in the history buffer. Users can use the "!history" command to list these messages.
Type	number (0–250)
Default	`20`
Since	uhub 0.3.0

max_logout_logdefault: 20

Description	Operators can use the "!log" command to list users who have recently left the hub. This option specifies the maximum size of this log.
Type	number (0–2000)
Default	`20`
Since	uhub 0.3.0

file_acldefault: ""

Description	An access control list (acl) file holding ban and deny rules only: ban_nick, ban_cid, deny_nick and deny_ip. If missing or empty, no such rules are loaded. IMPORTANT (changed in 0.8.0): registered users are NO LONGER defined here. Account credentials are served by an authentication plugin (mod_auth_simple / mod_auth_sqlite, configured via file_plugins). The old user_admin / user_super / user_op / user_reg / link / bot / ubot / opbot / opubot keywords, and nat_ip (now the nat_override option), are obsolete: they are ignored with a warning so existing files keep loading, but you must migrate them.
Type	file
Default	`""`
Since	uhub 0.1.3
Example	Unix users: file_acl = "/etc/uhub/users.conf" Windows users: file_acl = "c:\uhub\users.conf"

file_pluginsdefault: ""

Description	Plugin configuration file.
Type	file
Default	`""`
Since	uhub 0.3.3
Example	file_plugins = "/etc/uhub/plugins.conf"

Access control (users.conf)

These directives live in the ACL file (the file_acl path), not in uhub.conf.

Changed in 0.8.0: the ACL file holds ban and deny rules only. Registered accounts are no longer defined here — the user_admin, user_super, user_op, user_reg, link, bot, ubot, opbot and opubot keywords are obsolete, and so is nat_ip (replaced by the nat_override option in uhub.conf). Obsolete lines are ignored with a warning so an old file still loads, but they no longer do anything. Move accounts to an authentication plug-in — mod_auth_sqlite or mod_auth_simple — configured through file_plugins.

deny_nickusername

Description	A denied username. Any user identifying with this nickname is denied access.
Syntax	`deny_nick username`
Since	uhub 0.1.2
Example	`deny_nick Administrator deny_nick root deny_nick Hub-Security`

ban_nickusername

Description	A user banned by nickname. Differs from deny_nick in the message the user receives.
Syntax	`ban_nick username`

ban_cidcid

Description	A user banned by CID (a 39-byte base32-encoded client identifier).
Syntax	`ban_cid cid`
Since	uhub 0.1.2
Example	`ban_cid FOIL5EK2UDZYAXT7UIUFEKL4SEBEAJE3INJDKAY`

deny_ipip range/mask

Description	Deny access to users from certain IP addresses, given as ranges or address/bitmask. Works for IPv6 too.
Syntax	`deny_ip ip range/mask`
Since	uhub 0.1.2
Example	`deny_ip 192.168.0.0/24 deny_ip ::1/128`

Bans created at runtime with !ban (and lifted with !unban) are not written back to this file. To survive a restart they need a storage plug-in that implements ban persistence — see mod_auth_sqlite.

Message strings

msg_hub_fullstring

Description	This will be sent if the hub is full
Type	String
Default	`"Hub is full"`
Since	uhub 0.2.0

msg_hub_disabledstring

Description	This will be sent if the hub is disabled (hub_enable = off)
Type	String
Default	`"Hub is disabled"`
Since	uhub 0.2.0

msg_hub_registered_users_onlystring

Description	This will be sent if the hub is configured to only accept registered users (registered_users_only = yes)
Type	String
Default	`"Hub is for registered users only"`
Since	uhub 0.2.0

msg_inf_error_nick_missingstring

Description	This is an error message that will be sent to clients that do not provide a nickname.
Type	String
Default	`"No nickname given"`
Since	uhub 0.2.0

msg_inf_error_nick_multiplestring

Description	This is an error message that will be sent to clients that provide multiple nicknames.
Type	String
Default	`"Multiple nicknames given"`
Since	uhub 0.2.0

msg_inf_error_nick_invalidstring

Description	This is an error message that will be sent to clients that provides an invalid nickname.
Type	String
Default	`"Nickname is invalid"`
Since	uhub 0.2.0

msg_inf_error_nick_longstring

Description	This is an error message that will be sent to clients that provides a too long nickname.
Type	String
Default	`"Nickname too long"`
Since	uhub 0.2.0

msg_inf_error_nick_shortstring

Description	This is an error message that will be sent to clients that provides a too short nickname.
Type	String
Default	`"Nickname too short"`
Since	uhub 0.2.0

msg_inf_error_nick_spacesstring

Description	This is an error message that will be sent to clients that provides a nickname that starts with a space.
Type	String
Default	`"Nickname cannot start with spaces"`
Since	uhub 0.2.0

msg_inf_error_nick_bad_charsstring

Description	This is an error message that will be sent to clients that provides invalid characters in the nickname.
Type	String
Default	`"Nickname contains invalid characters"`
Since	uhub 0.2.0

msg_inf_error_nick_not_utf8string

Description	This is an error message that will be sent to clients that provides a nick name that is not valid UTF-8 encoded.
Type	String
Default	`"Nickname is not valid UTF-8"`
Since	uhub 0.2.0

msg_inf_error_nick_takenstring

Description	This message will be sent to clients if their provided nickname is already in use on the hub.
Type	String
Default	`"Nickname is already in use"`
Since	uhub 0.2.0

msg_inf_error_nick_restrictedstring

Description	This message will be sent to clients if they provide a restricted nickname. Restricted names can be configured in the acl.
Type	String
Default	`"Nickname cannot be used on this hub"`
Since	uhub 0.2.0

msg_inf_error_cid_invalidstring

Description	This is an error message that will be sent to clients that provides an invalid client ID (CID)
Type	String
Default	`"CID is not valid"`
Since	uhub 0.2.0

msg_inf_error_cid_missingstring

Description	This is an error message that will be sent to clients that does not provide a client ID (CID)
Type	String
Default	`"CID is not specified"`
Since	uhub 0.2.0

msg_inf_error_cid_takenstring

Description	This is an error message that will be sent to clients that provides a client ID (CID) already in use on the hub.
Type	String
Default	`"CID is taken"`
Since	uhub 0.2.0

msg_inf_error_pid_missingstring

Description	This is an error message that will be sent to clients that does not provide a private ID (PID)
Type	String
Default	`"PID is not specified"`
Since	uhub 0.2.0

msg_inf_error_pid_invalidstring

Description	This is an error message that will be sent to clients that provides an invalid private ID (PID)
Type	String
Default	`"PID is invalid"`
Since	uhub 0.2.0

msg_ban_permanentlystring

Description	This message is sent to users if they are banned (see acl)
Type	String
Default	`"Banned permanently"`
Since	uhub 0.2.0

msg_ban_temporarilystring

Description	This message is sent to users if they are banned temporarily
Type	String
Default	`"Banned temporarily"`
Since	uhub 0.2.0

msg_auth_invalid_passwordstring

Description	This message is sent to users if they provide a wrong password.
Type	String
Default	`"Password is wrong"`
Since	uhub 0.2.0

msg_auth_user_not_foundstring

Description	This message is used if a user cannot be found in the password database.
Type	String
Default	`"User not found in password database"`
Since	uhub 0.2.0

msg_error_no_memorystring

Description	Hub has no more memory
Type	String
Default	`"No memory"`
Since	uhub 0.2.0

msg_user_share_size_lowstring

Description	This message is sent to users if they are not sharing enough.
Type	String
Default	`"User is not sharing enough"`
Since	uhub 0.2.0

msg_user_share_size_highstring

Description	This message is sent to users if they are sharing too much.
Type	String
Default	`"User is sharing too much"`
Since	uhub 0.2.0

msg_user_slots_lowstring

Description	This message is sent to users if they do not have enough upload slots.
Type	String
Default	`"User have too few upload slots."`
Since	uhub 0.2.0

msg_user_slots_highstring

Description	This message is sent to users if they have too many upload slots.
Type	String
Default	`"User have too many upload slots."`
Since	uhub 0.2.0

msg_user_hub_limit_lowstring

Description	This message is sent to users if they are on too few other hubs.
Type	String
Default	`"User is on too few hubs."`
Since	uhub 0.2.0

msg_user_hub_limit_highstring

Description	This message is sent to users if they are on too many other hubs.
Type	String
Default	`"User is on too many hubs."`
Since	uhub 0.2.0

msg_user_flood_chatstring

Description	This message is sent once to users who are flooding the chat.
Type	String
Default	`"Chat flood detected, messages are dropped."`
Since	uhub 0.3.1

msg_user_flood_connectstring

Description	This message is sent once to users who are sending too many connect requests too fast.
Type	String
Default	`"Connect flood detected, connection refused."`
Since	uhub 0.3.1

msg_user_flood_searchstring

Description	This message is sent once to users who are sending too many search requests too fast.
Type	String
Default	`"Search flood detected, search is stopped."`
Since	uhub 0.3.1

msg_search_too_shortstring

Description	This message is sent to users whose search term is shorter than limit_min_search.
Type	String
Default	`"Search term is too short."`
Since	uhub 0.7.0

msg_user_flood_updatestring

Description	This message is sent once to users who are sending too many updates too fast.
Type	String
Default	`"Update flood detected."`
Since	uhub 0.3.1

msg_user_flood_extrasstring

Description	This message is sent once to users who are sending too many messages to the hub that neither are chat, searhes, updates nor connection requests..
Type	String
Default	`"Flood detected."`
Since	uhub 0.3.1

msg_chat_is_privilegedstring

Description	This message is sent to unprivileged users who try to chat when chat_is_privileged is enabled.
Type	String
Default	`"Chat is reserved for operators and above."`
Since	uhub 0.5.1

msg_proto_no_common_hashstring

Description	This message is sent if a client connects that does support ADC/1.0 but not a hash algorithm that the hub supports.
Type	String
Default	`"No common hash algorithm."`
Since	uhub 0.3.1

msg_proto_obsolete_adc0string

Description	This message is sent if a client connects that does not support ADC/1.0, but rather the obsolete ADC/0.1 version.
Type	String
Default	`"Client is using an obsolete ADC protocol version."`
Since	uhub 0.3.1