UDP (im_udp)
This module accepts UDP datagrams on the configured address and port. UDP is the transport protocol of the legacy BSD Syslog as described in RFC 3164, so this module can be particularly useful to receive such messages from older devices that do not support other transports.
| UDP is an unreliable transport protocol and does not guarantee delivery. Messages may not be received or may be truncated. It is recommended to use the TCP or SSL transport modules instead, if possible. |
To reduce the likelihood of message loss, consider:
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increasing the socket buffer size with SockBufSize,
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raising the route priority by setting the Priority directive (to a low number such as 1), and
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adding additional buffering by increasing the LogqueueSize or adding a pm_buffer instance.
| This module does not provide access control. Firewall rules can be used to deny connections from certain hosts. |
For parsing syslog messages, see the parse_syslog_bsd() procedure of the xm_syslog module.
Configuration
The im_udp module accepts the following directives in addition to the common module directives.
Optional directives
The module accepts connections on the IP address or hostname and port defined here.
The default address is To listen on multiple addresses or ports in a single module instance, this directive can be repeated multiple times. Both IPv4 and IPv6 addresses are supported. If a DNS name is used, the number of addresses or cnames should be kept below 16 to avoid potential issues caused by DNS response size limits.
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This optional directive can be used to allow IP addresses and/or networks to connect. The directive can be set multiple times to add different IPs or networks to allow. This directive is only active when the ListenAddr directive is present. In the absence of this directive, the BlockIP directive is considered. If both AllowIP and BlockIP are absent, then hosts are not restricted from connecting to a listening module. The following formats may be used for the AllowIP directive:
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This optional directive can be used to deny IP addresses and/or networks to connect. The directive can be set multiple times to add different IPs or networks to deny. This directive is only active when the ListenAddr directive is present. In the absence of this directive, the AllowIP directive is considered. If both AllowIP and BlockIP are absent, then hosts are not restricted from connecting to a listening module. The following formats may be used for the BlockIP directive:
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This optional boolean directive specifies whether the module instance should exclusively bind to the specified port.
The default value is
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This optional boolean directive determines whether the module instance should forcibly bind to a port already in use.
The default value is |
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This optional boolean directive specifies whether multiple im_udp module instances can listen on the same port.
When you enable this directive, multiple instances run in a separate thread, allowing NXLog Agent to process incoming logs simultaneously.
See the examples below.
The default value is
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This optional directive sets the socket buffer size (SO_RCVBUF) to the value specified.
If not set, the operating system defaults are used.
If UDP packet loss is occurring at the kernel level, setting this to a high value (such as |
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This boolean directive specifies that the |
Examples
This configuration accepts log messages via UDP and writes them to a file.
<Input udp>
Module im_udp
ListenAddr 192.168.1.1:514
</Input>
<Output file>
Module om_file
File "tmp/output"
</Output>
<Route udp_to_file>
Path udp => file
</Route>The configuration below provides two im_udp module instances to reuse port 514 via the ReusePort directive.
Received messages are written to the /tmp/output file.
<Input udp_one>
Module im_udp
ListenAddr 192.168.1.1:514
ReusePort TRUE
</Input>
<Input udp_two>
Module im_udp
ListenAddr 192.168.1.1:514
ReusePort TRUE
</Input>
<Output file>
Module om_file
File "tmp/output"
</Output>
<Route udp_to_file>
Path udp_one, udp_two => file
</Route>