Plan 9 - man page for ip (plan9 section 3)
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ip - TCP, UDP, IL network protocols over IP
bind -a #Itcp /net
bind -a #Iudp /net
bind -a #Iil /net
The IP device provides the interface for several protocols that run over IP on an Ether-
net. TCP and UDP provide the standard Internet protocols for reliable stream and unreli-
able datagram communication. IL provides a reliable datagram service for communication
between Plan 9 machines. IL is the protocol of choice for most Plan 9 services.
Each of the protocols is served by the IP device, which represents each connection by a
set of device files. The top level directory of each protocol contains a clone file and
subdirectories numbered from zero to the number of connections configured for this proto-
Opening the clone file reserves a connection. The file descriptor returned from the
open(2) will point to the control file, ctl, of the newly allocated connection. Reading
the ctl file returns a text string representing the number of the connection. Connections
may be used either to listen for incoming calls or to initiate calls to other machines.
A connection is controlled by writing text strings to the associated ctl file. After a
connection has been established data may be read from and written to the data file. For
the datagram services, IL and UDP, a read of less than the length of a datagram will cause
the entire datagram to be consumed. Each write to the data file will send a single data-
gram on the network. The TCP protocol provides a stream connection that does not preserve
Prior to sending data, remote and local addresses must be set for the connection. For
outgoing calls the local port number will be allocated randomly if none is set. Addresses
are set by writing control messages to the ctl file of the connection. The connection is
not established until the data file is opened. For IL and TCP the process will block
until the remote host has acknowledged the connection. UDP opens always succeed.
The following control messages are supported:
Set the remote IP address and port number for the connection. If the r flag is
supplied and no local address has been specified the system will allocate a
restricted port number (less than 1024) for the connection to allow communication
with Unix machines' login and exec services.
(UDP only) Clear the remote address of a UDP connection.
X is a decimal port number or Set the local port number to X and accept calls to X.
If X is accept calls for any port that no process has explicitly announced. The
local IP address cannot be set. Announce fails if the connection is already
announced or connnected.
bind X X is a decimal port number or Set the local port number to X. This exists to sup-
port library emulation of BSD sockets and is not otherwise used.
(IL and TCP only) Set the maximum number of pending requests for a given service to
n. By default n is set to five. If more than n connections are pending, further
requests for a service will be rejected.
Port numbers must be in the range 1 to 32767. If a local port has not been announced
prior to a connect a local port number will be allocated automatically. Local ports are
allocated from 5000 up.
Several files report the status of a connection. The remote and local files contain the
IP address and port number for the remote and local side of the connection. The status
file contains protocol-dependent information to help debug network connections.
A process may accept incoming connections by calling open on the listen file. The open
will block until a new connection request arrives. Then open will return an open file
descriptor which points to the control file of the newly accepted connection. This proce-
dure will accept all calls for the given protocol.
listen(8), dial(2), ndb(6)
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