KNEWS(1) General Commands Manual KNEWS(1)NAME
tcp_relay - a tcp relay
SYNOPSIS
tcp_relay -p port [-s] -h host ... remotehost[:port]
DESCRIPTION
For more details, read the source.
OPTIONS -p port
The port tcp_relay will listen for connections on.
-s
If this option is given, only a single connection at a time will be handled. Otherwise tcp_relay will fork a new copy of itself for
each incomming connection and go on to accept new connections.
-h host
Connections from this host will be allowed. Several of these may be supplied.
AUTHOR
This software is Copyright 1996 by Karl-Johan Johnsson.
1996 KNEWS(1)
Check Out this Related Man Page
IP(3) Library Functions Manual IP(3)NAME
ip - TCP, UDP, IL network protocols over IP
SYNOPSIS
bind -a #Itcp /net
bind -a #Iudp /net
bind -a #Iil /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 several protocols that run over IP on an Ethernet. TCP and UDP provide the standard Internet pro-
tocols for reliable stream and unreliable 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 protocol.
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 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 allo-
cated 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:
connect ipaddress!port[!r]
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.
disconnect
(UDP only) Clear the remote address of a UDP connection.
announce X
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 support library emulation of BSD sockets and is not
otherwise used.
backlog n
(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 allo-
cated 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 procedure will
accept all calls for the given protocol.
SEE ALSO listen(8), dial(2), ndb(6)SOURCE
/sys/src/9/port/devip.c
/sys/src/9/port/stil.c
/sys/src/9/port/stip.c
/sys/src/9/port/tcp*.c
IP(3)