ip - TCP, UDP network protocols over IP

bind -a '#I' /net

/net/tcp/clone
/net/tcp/<n>
/net/tcp/<n>/data
/net/tcp/<n>/ctl
/net/tcp/<n>/local
/net/tcp/<n>/remote
/net/tcp/<n>/status
/net/tcp/<n>/listen
...

Description

The IP device provides the interface for protocols that run over IP. TCP and UDP provide the standard internet protocols for reliable stream and unreliable datagram communication.

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 0 to the number of connections configured for this protocol.

clone

Opening the clone file reserves a connection. The file descriptor returned from the open call points to the control file, ctl, of the newly allocated connection.

ctl

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.

data

After a connection has been established data may be read from and written to the data file. For the datagram service UDP, a read of less than the length of a datagram causes the entire datagram to be consumed. Each write to the data file sends a single datagram on the network. The TCP protocol provides a stream connection that does not preserve read/write boundaries.

clone	Opening the clone file reserves a connection. The file descriptor returned from the open call points to the control file, ctl, of the newly allocated connection.
ctl	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.
data	After a connection has been established data may be read from and written to the data file. For the datagram service UDP, a read of less than the length of a datagram causes the entire datagram to be consumed. Each write to the data file sends a single datagram on the network. The TCP protocol provides a stream connection that does not preserve read/write boundaries.

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 TCP, the process will block until the remote host has acknowledged the connection. UDP opens always succeed.

Notes

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 is automatically allocated. Local ports are numbers greater than or equal to 5000.

Several files report the status of a connection.

remote

The remote file provides the IP address and port number for the remote side of the connection.

local

The local files contain the IP address and port number for the local side of the connection.

status

The status file contains protocol-dependent information to help debug network connections.

listen

A process may accept incoming connections by opening the listen file. The open will block until a new connection request arrives. Then open will return an open file descriptor that points to the control file of the newly accepted connection. This procedure accepts all calls for the given protocol.

remote	The remote file provides the IP address and port number for the remote side of the connection.
local	The local files contain the IP address and port number for the local side of the connection.
status	The status file contains protocol-dependent information to help debug network connections.
listen	A process may accept incoming connections by opening the listen file. The open will block until a new connection request arrives. Then open will return an open file descriptor that points to the control file of the newly accepted connection. This procedure accepts all calls for the given protocol.

The dial, announce, and listen functions in the Sys module provide an alternate method to perform the necessary I/O to establish and manipulate network connections.