Provided by: ser2net_3.5-2_amd64 
NAME
ser2net - Serial to network proxy
SYNOPSIS
ser2net [-c configfile] [-C configline] [-p controlport] [-n] [-d] [-b] [-v] [-P pidfile]
DESCRIPTION
The ser2net daemon allows telnet and tcp sessions to be established with a unit's serial
ports or with an IPMI Serial Over LAN (SOL) interface.
The program comes up normally as a daemon, opens the network ports specified in the
configuration file, and waits for connections. Once a connection occurs, the program
attempts to set up the connection and open the serial port. If another user is already
using the connection or serial port, the connection is refused with an error message.
OPTIONS
-c config-file
Set the configuration file to one other than the default of /etc/ser2net.conf
-C config-line
Handle a single configuration line. This may be specified multiple times for
multiple lines. This is just like a line in the config file. This disables the
default config file, you must specify a -c after the last -C to have it read a
config file, too.
-n Stops the daemon from forking and detaching from the controlling terminal.
This is useful for running from init.
-d Like -n, but also sends the system logs to standard output. This is most useful for
debugging purposes.
-P pidfile
If specified, put the process id (pid) of ser2net in the pidfile, replacing
whatever was in that file previously. A pidfile is not created by default, you
must specify this to create one. Note also that this filename must be specific
with the full path, as ser2net will change directory to "/" when it becomes a
daemon. when it
-u If UUCP locking is enabled, this will disable the use of UUCP locks.
-b Cisco IOS uses a different mechanism for specifying the baud rates than the
mechanism described in RFC2217. This option sets the IOS version of setting the
baud rates. The default is RFC2217's. Note that this capability is now handled
automatically and this option is ignored.
-v Prints the version of the program and exits.
-t <num threads>
Spawn the given number of threads for ser2net to use. The default is 1. Only
valid if pthreads is enabled at build time.
-p controlport
Enables the control port and sets the TCP port to listen to for the control port.
A port number may be of the form [host,]port, such as 127.0.0.1,2000 or
localhost,2000. If this is specified, it will only bind to the IP address
specified for the port. Otherwise, it will bind to all the addresses on the
machine.
If the port number is zero, that means that standard in/out will be used for the
only input/output, and only one port should be specified in the config. This way,
it can be used from inetd.
-s signature
Specifies the default RFC2217 signature.
CONTROL PORT
The control port provides a simple interface for controlling the ports and viewing their
status. To accomplish this, it has the following commands:
showport [<network port>]
Show information about a port. If no port is given, all ports are displayed.
showshortport [<network port>]
Show information about a port, each port on one line. If no port is given, all
ports are displayed. This can produce very wide output.
help Display a short list and summary of commands.
exit Disconnect from the control port.
version
Display the version of this program.
monitor <type> <network port>
Display all the input for a given port on the calling control port. Only one
direction may be monitored at a time. The type field may be tcp or term and
specifies whether to monitor data from the network port or from the serial port
Note that data monitoring is best effort, if the controller port cannot keep up the
data will be silently dropped. A controller may only monitor one thing and a port
may only be monitored by one controller.
monitor stop
Stop the current monitor.
disconnect <network port>
Disconnect the tcp connection on the port.
setporttimeout <network port> <timeout>
Set the amount of time in seconds before the port connection will be shut down if
no activity has been seen on the port.
setportconfig <network port> <config>
Set the port configuration as in the device configuration in the /etc/ser2net.conf
file. If conflicting options are specified, the last option will be the one used.
Note that these will not change until the port is disconnected and connected again.
Options 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 set the various
baud rates. The following speed may be available if your system has the values
defined and your hardware supports it: 230400, 460800, 500000, 576000, 921600,
1000000, 1152000, 1500000, 2000000, 2500000, 3000000, 3500000, 4000000. EVEN, ODD,
NONE (MARK and SPACE if supported) set the parity. 1STOPBIT, 2STOPBITS set the
number of stop bits. 7DATABITS, 8DATABITS set the number of data bits. [-]XONXOFF
turns on (- off) XON/XOFF support. [-]RTSCTS turns on (- off) hardware flow
control. [-]LOCAL ignores (- checks) the modem control lines (DCD, DTR, etc.)
setportcontrol <network port> <controls>
Modify dynamic port controls. These do not stay between connections. Controls
are: DTRHI, DTRLO Turns on and off the DTR line. RTSHI, RTSLO Turns on and off the
RTS line.
setportenable <network port> <enable state>
Sets the port operation state. Valid states are: off to shut the network port
down, raw to enable the network port transfer all I/O as-is, rawlp to enable the
network port input and device output without termios setting, and telnet to enable
the network port is up run the telnet negotiation protocol on the port.
CONFIGURATION
Configuration is accomplished through the file /etc/ser2net.conf. A file with another
name or path may be specified using the -c option, or individual config lines may be
specified with the -C option. This file consists of one or more entries with the
following format:
<network port>:<state>:<timeout>:<device>:<options>
or
BANNER:<banner name>:<banner text>
or
SIGNATURE:<signature name>:<signature text>
or
OPENSTR:<openstr name>:<openstr text>
or
CLOSESTR:<closestr name>:<closestr text>
or
CLOSEON:<closeon name>:<closeon text>
or
TRACEFILE:<tracefile name>:<tracefile>
or
CONTROLPORT:<port spec>
or
DEVICE:<name>:<device>
or
DEFAULT:<parm>:<defaultval>
or
ROTATOR:<TCP port>:<port list>
or
LED:<led-name>:<driver>:<parameters>
A line that ends in '\' (it must be the very last character) is continued on the next
line. There is no arbitrary maximum line length.
FIELDS
network port
Name or number of the network port to accept connections from for this device. A
port number may be of the form [ipv4,|ipv6,][tcp,|udp,][host,]port, such as
127.0.0.1,2000 or ipv4,localhost,2000, or udp,::,2000. If host is specified, it
will only bind to the IP address specified for the port. Otherwise, it will bind
to all the ports on the machine. You can specify an IPV6 address in the port, any
colon before the comma is ignored for parsing fields. If ipv4 or ipv6 is
specified, it will only bind to that network type.
If udp is specified, any data received on the port from a remote source is
considered a "connection" and the data for that port will go back to the remote
source address. See the later section on UDP for details.
state Either raw or rawlp or telnet or off. off disables the port from accepting
connections. It can be turned on later from the control port. raw enables the
port and transfers all data as-is between the port and the long. rawlp enables the
port and transfers all input data to device, device is open without any termios
setting. It allow to use /dev/lpX devices and printers connected to them. telnet
enables the port and runs the telnet protocol on the port to set up telnet
parameters. This is most useful for using telnet.
timeout
The time (in seconds) before the port will be disconnected if there is no activity
on it. A zero value disables this function.
device The name of the device to connect to. This must be in the form of
/dev/<device> or sol.<solparms>. For SOL parameters, see the solterm man page that
is part of openipmi. This may be specified in a DEVICE directive, then you can use
the name in the DEVICE directive to specify the device in the DEVICE directive.
This can be used to give shorter and/or meaningful names for devices, or to allow
special characters (like a colon) in the device name.
device configuration options
Sets operational parameters for the serial port. Values are be separated by
spaces. Options 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 set the
various baud rates for serial device and SOL ports. The following speed may be
available if your system has the values defined and your hardware supports it:
230400, 460800, 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
2500000, 3000000, 3500000, 4000000. Note that only a limited set are available on
SOL. [-]NOBREAK disables automatic clearing of the break setting of the port.
Available on serial device and SOL ports.
EVEN, ODD, NONE (MARK and SPACE if supported) set the parity. (serial device only)
Note that MARK and SPACE are not available on all systems or hardware, if it is not
supported then it will be silently set to ODD or EVEN parity. 1STOPBIT, 2STOPBITS
set the number of stop bits. (serial device only) 5DATABITS, 6DATABITS, 7DATABITS,
8DATABITS set the number of data bits. (serial device only) [-]XONXOFF turns on (-
off) XON/XOFF support. (serial device only) [-]RTSCTS turns on (- off) hardware
flow control. (serial device only) [-]LOCAL ignores (- checks) the modem control
lines (DCD, DTR, etc.) (serial device only) [-]HANGUP_WHEN_DONE lowers (- does not
lower) the modem control lines (DCD, DTR, etc.) when the connection closes. (serial
device only) [-]remctl allows remote control of the serial port parameters via RFC
2217. See the README for more info. [-]kickolduser sets the port so that the
previous user will be kicked off if a new user comes in. Useful if you forget to
log off from someplace else a lot. <banner name> displays the given banner when a
user connects to the port. <signature name> sends RFC2217 signature on clients
request. <openstr name> Send the given string to the device when the port is
opened. <closestr name> Send the given string to the device when the port is
closed.
tr=<filename> When the port is opened, open the given tracefile and store all data
read from the physical device (and thus written to the user's TCP port) in the
file. The actual filename is specified in the TRACEFILE directive. If the file
already exists, it is appended. The file is closed when the port is closed.
tw=<filename> Like tr, but traces data written to the device.
tb=<filename> trace both read and written data to the same file. Note that this is
independent of tr and tw, so you may be tracing read, write, and both to different
files.
[-]hexdump turns on (- turns off) hexdump output to all trace files. Each line in
the trace file will be 8 (or less) bytes in canonical hex+ASCII format. This is
useful for debugging a binary protocol.
[-]timestamp adds (- removes) a timestamp to all of the trace files. A timestamp is
prepended to each line if hexdump is active for the trace file. A timestamped line
is also recorded in the trace file when a remote client connects or disconnects
from the port.
[-][tr-|tw-|tb-]hexdump turns on (- turns off) hexdump output for only one trace
file. May be combined with [-]hexdump. Order is important.
[-][tr-|tw-|tb-]timestamp adds (- removes) a timestamp to only one the trace files
May be combined with [-]timestamp. Order is important.
[-]telnet_brk_on_sync causes a telnet sync operation to send a break. By default
data is flushed until the data mark, but no break is sent.
[-]disable-chardelay disables the small wait after each character received on the
serial port before sending data on the TCP port. Normally ser2net will wait the
time it takes to receive 2 serial port characters, or at least 1000us, before
sending on the TCP port. This allows more efficient use of network resources when
receiving large amounts of data, but gives reasonable interactivity.
chardelay-scale=<number> sets the number of serial port characters, in tenths of a
character, to wait after receiving from the serial port and sending to the TCP
port. So setting this to 25 will cause ser2net to wait the amount of time it takes
to recieve 2.5 serial port characters before sending the data on to the TCP port.
The default value is 20.
chardelay-min=<number> sets the minimum delay that ser2net will wait, in
microseconds. If the calculation for chardelay-scale results in a value smaller
than this number, this number will be used instead. The default value is 1000.
chardelay-max=<number> sets the maximum delay that ser2net will wait, in
microseconds, before sending the data. The default value is 20000. This keeps the
connection working smoothly at slow speeds.
dev-to-net-bufsize=<number> sets the size of the buffer reading from the serial
device and writing to the network port.
net-to-dev-bufsize=<number> sets the size of the buffer reading from the network
port and writing to the serial device.
[-]authenticated enable (-disable) authentication on the link. (SOL only)
[-]encrypted enable (-disable) encryption on the link. (SOL only)
shared_serial_alert_fail fail the connection if the serial port is in use through
hardware. (SOL only)
shared_serial_alert_deferred if the serial port is already in use through hardware,
wait until it is released. (SOL only)
shared_serial_alert_deferred if the serial port is already in use via hardware,
take over the connection. (SOL only)
[-]deassert_CTS_DCD_DSR_on_connect deassert (- do not deassert) the given serial
signals on a SOL connection. (SOL only)
ack-timeout=n set the timeout for resending to n microseconds. (SOL only)
ack-retries=n set the number of retries before failure to n times. (SOL only)
<parm> is a parameter to set a default for. When you set a default, it sets the
default value for all following config lines. Available parameters are: speed,
databits, stopbits, parity, xonxoff, rtscts, local, hangup_when_done, nobreak,
remctl, telnet_brk_on_sync, kickolduser, chardelay, chardelay-scale, chardelay-min,
and chardelay-max. See ser2net.conf for details.
<defaultval> The default value to set the parameter.
<port list> A space separated list of ports. When connecting to the given TCP
port, ser2net will go through the port list until it finds a free one and attempt
to connect to that port.
led-tx=<led-name> use the previously defined led to indicate serial tx traffic on
this port.
led-rx=<led-name> use the previously defined led to indicate serial rx traffic on
this port.
max-connections=<number> set the maximum number of connections that can be made on
this particular TCP port. If you make more than one connection to the same port,
each ports output goes to the device, and the device output goes to all ports
simultaneously. See "MULTIPLE CONNECTIONS" below for details. The default is 1.
remaddr=<addr>[;<addr>[;...]] specifies the allowed remote connections, where the
addr is a standard address in the form (see "network port" above). Multiple
addresses can be separated by semicolons, and you can specify remaddr more than
once. If you set the port for an address to zero, ser2net will accept a connection
from any port from the given network host.
banner name
A name for the banner; this may be used in the options of a port.
banner text
The text to display as the banner. It takes escape sequences for substituting
strings, see "FILENAME, BANNER, AND STRING FORMATTING" for details.
tracefile name
A name for the tracefile, this is used in the tw, tr, and tb options of a port.
tracefile
The file to send the trace into. Note that this takes escape sequences for
substituting strings, see "FILENAME, BANNER, AND STRING FORMATTING" for details.
Note that when using the time escape sequences, the time is read once at port
startup, so if you use both tw and tr they will have the same date and time.
port spec
The control port specification as defined by the [-p] option on the command line.
This lets the control port be specified in the configuration file. The command
line will override this, and only the first port specified is used.
led Define an LED with given name. At the moment, the only available driver is "sysfs"
which uses a Linux's LED class device (/sys/class/leds/<device>) and configures it
for transient LED trigger. It knows about the required parameter "device" which
specifies which LED class device to use (the directory name of the LED below
/sys/class/leds). The optional "duration" parameter controls the length of the
flash pulse in milliseconds and defaults to 10. The optional parameter "state"
controls whether the LED is off/on when the timer is active. It takes 0 or 1 as
values and defaults to 1. See ledtrig-transient.txt in Linux kernel documentation
for more details.
The transient trigger must be compiled into the kernel or already loaded as kernel
module.
Individual network ports can refer to this LED and thus trigger flashing of this
LED when tx/rx traffic is seen.
Blank lines and lines starting with `#' are ignored.
FILENAME, BANNER, AND STRING FORMATTING
Filenames, banners, and open/close string may contain normal "C" escape sequences and a
large number of other escape sequences, too:
\a - bell
\b - backspace
\f - form feed
\n - newline
\r - carriage return
\t - tab
\v - vertical tab
\\ - \
\? - ?
\' - '
\" - "
\nnn - octal value for nnn
\xXX - hex value for XX
\d - The device name (/dev/ttyS0, etc.)
\p - Network port number
\B - The serial port parameters (eg 9600N81)
\Y -> year
\y -> day of the year (days since Jan 1)
\M -> month (Jan, Feb, Mar, etc.)
\m -> month (as a number)
\A -> day of the week (Mon, Tue, etc.)
\D -> day of the month
\e -> epoc (seconds since Jan 1, 1970)
\U -> microseconds in the current second
\p -> local port number
\d -> local device name
\I -> remote IP address (in dot format)
\H -> hour (24-hour time)
\h -> hour (12-hour time)
\i -> minute
\S -> second
\q -> am/pm
\P -> AM/PM
In addition, for backwards compatibility because filenames and banners used to have
different formatting, \s is the serial port parameters if in a banner and seconds if in a
filename. Use of this is discouraged as it may change in the future.
These sequences may be used to make the filename unique per open and identify which
port/device the filename was for. Note that in filenames when using \d, everything up to
and including last / in the device name is removed, because you can't have a / in a
filename. So in a filename /dev/ttyS0 would become just ttyS0.
UDP
UDP handling is a bit different than you might imagine, because it's hard for ser2net to
know where to send the data to. To handle this, UDP ports still have the concept of a
"connection". If a UDP port is not connected, then if it received a packet the remote
address for that packet is set to the remote end of the "connection". It will do all the
normal new connection operations. ser2net will then ignore packets from other addresses
until a disconnect occurs.
Unfortunately, there is no easy way to know when to disconnect. You have two basic
options:
Set a timeout, if the remote end isn't heard from before the timeout, then the port
is disconnected and something else can connect. This means anything that is using
the port must periodically send a packet (empty is find) to ser2net to keep the
connection alive.
Use the kickolduser option on the port, any new connection that comes in will
replace the previous connection.
Note that UDP ports handle multiple connections just like TCP ports, so you can have
multiple UDP listeners.
You also have a third option. If you set a remote address (remaddr) with a non-zero port,
ser2net will take one of the connections and assign it to that port permanently. This is
called a fixed remote address. All the traffic from the device will go to that port.
Every fixed remote address on a UDP port has to have a corresponding connection, so if you
have 3 fixed remote addresses, you must have at least 3 connections.
MULTIPLE CONNECTIONS
As mentioned earlier, you can set max-connections=<n> on a port to allow more than one
connection at a time to the same serial port. These connections will share all the
settings. You cannot have two separate TCP ports connect to the same port at the same
time.
This has some significant interactions with other features:
flow control is not exactly a feature, but more an interaction between the different
connections. If a TCP port stops receiving data from ser2net, all TCP ports connected
will be flow-controlled. This means a single TCP connection can stop all the others.
closeon will close all connections when the closeon sequence is seen.
openstr is only sent when the port is unconnected and the first connections is made.
closestr is only sent when the last port disconnects and there are no more connections to
the port.
Any monitor ("monitor start" from a control connections) will catch input from all network
connections.
kickolduser will kick off all connections if a connection comes in on a port that already
has a maximum number of connections.
tracing will trace data from all network connections.
remctl (remote telnet serial control) will change the connection settings on the device
and will be accepted from any network connection.
ROTATOR will only choose a port if there are no connections at all on the port. Note that
the use of a rotator with a port with max-connections > 1 will result in undefined
behavior.
timeout will be per TCP port and will only disconnect that TCP port on a timeout.
telnet_brk_on_sync will send a break for any TCP port that does a sync.
showport will show all possible connections, so if you say max-connections=3 you will get
three entries.
showshortport will only show the first live connection, or if no connection is present it
will show whatever the first one was the last time a connection was present.
SECURITY
ser2net uses the tcp wrappers interface to implement host-based security. See
hosts_access(5) for a description of the file setup. Two daemons are used by ser2net,
"ser2net" is for the data ports and "ser2net-control" is for the control ports.
SIGNALS
SIGHUP
If ser2net receives a SIGHUP, it will reread it configuration file and make the
appropriate changes. If an inuse port is changed or deleted, the actual change will
not occur until the port is disconnected.
Error
Almost all error output goes to syslog, not standard output.
FILES
/etc/ser2net.conf
SEE ALSO
telnet(1), hosts_access(5)
KNOWN PROBLEMS
None.
AUTHOR
Corey Minyard <minyard@acm.org>