udp(n) Tnm Tcl Extension udp(n)
__________________________________________________________________________________________________________________________________________________NAME
udp - Send and receive UDP datagrams.
_________________________________________________________________DESCRIPTION
The udp command allows to send and receive datagrams using the User Datagram Protocol (UDP) (RFC 768).
UDP COMMAND
udp open [port]
The udp open command opens a UDP datagram socket and returns an udp handle. The socket is bound to given port number or name. An
unused port number is used if the port argument is missing.
udp connect host port
The udp connect command opens a UDP datagram socket and connects it to a port on a remote host. A connected UDP socket only allows
to send messages to a single destination. This usually allows to shorten the code since there is no need to specify the destination
address for each udp send command on a connected UDP socket. The command returns a udp handle.
udp send handle [host port] message
The udp send command sends a datagram containing message to the destination specified by host and port. The host and port arguments
may not be used if the UDP handle is already connected to a transport endpoint. If the UDP handle is not connected, you must use
these optional arguments to specify the destination of the datagram.
udp receive handle
The udp receive command receives a datagram from the UDP socket associated with handle. This command blocks until a datagram is
ready to be received. In most cases, it might be a good idea to check for pending datagrams using the udp bind command.
udp close handle
The udp close command closes the UDP socket associated with handle.
udp bind handle readable [script]
udp bind handle writable [script]
The udp bind command allows to bind scripts to a UDP handle. A script is evaluated once the UDP handle becomes either readable or
writable, depending on the third argument of the udp bind command. The script currently bound to a UDP handle can be retrieved by
calling the udp bind command without a script argument. Bindings are removed by binding an empty string.
udp info [handle]
The udp info command without the handle argument returns a list of all existing UDP handles. Information about the state of a UDP
handle can be obtained by supplying a valid UDP handle. The result is a list containing the source IP address, the source port, the
destination IP address and the destination port.
SEE ALSO scotty(1), Tnm(n), Tcl(n)
AUTHORS
Juergen Schoenwaelder <schoenw@cs.utwente.nl>
Tnm udp(n)
Check Out this Related Man Page
UDP(4) BSD Kernel Interfaces Manual UDP(4)NAME
udp -- Internet User Datagram Protocol
SYNOPSIS
#include <sys/socket.h>
#include <netinet/in.h>
int
socket(AF_INET, SOCK_DGRAM, 0);
int
socket(AF_INET6, SOCK_DGRAM, 0);
DESCRIPTION
UDP is a simple, unreliable datagram protocol which is used to support the SOCK_DGRAM abstraction for the Internet protocol family. UDP
sockets are connectionless, and are normally used with the sendto(2) and recvfrom(2) calls, though the connect(2) call may also be used to
fix the destination for future packets (in which case the recv(2) or read(2) and send(2) or write(2) system calls may be used).
UDP address formats are identical to those used by TCP. In particular UDP provides a port identifier in addition to the normal Internet
address format. Note that the UDP port space is separate from the TCP port space (i.e. a UDP port may not be ``connected'' to a TCP port).
In addition broadcast packets may be sent (assuming the underlying network supports this) by using a reserved ``broadcast address''; this
address is network interface dependent.
There are two UDP-level setsockopt(2)/getsockopt(2) options. UDP_OPTIONS may be used to change the default behavior of the socket. For
example:
setsockopt(s, IPPROTO_UDP, UDP_OPTIONS, NULL, 0);
The UDP_ENCAP option can be used to encapsulate ESP packets in UDP. There are two valid enapsulation options: UDP_ENCAP_ESPINUDP_NON_IKE
from draft-ietf-ipsec-nat-t-ike-00/01 and UDP_ENCAP_ESPINUDP from draft-ietf-ipsec-udp-encaps-06 defined in <netinet/udp.h>.
The UDP_RFC6056ALGO can be used to randomize the port selection. Valid algorithms are described in rfc6056(7) and their respective constants
are in <netinet/rfc6056.h>. For example,
int algo = RFC6056_ALGO_RANDOM_PICK; /* see <netinet/rfc6056.h> */
setsockopt(s, IPPROTO_UDP, UDP_RFC6056ALGO, &algo, sizeof(algo));
The port selection can be also controlled at a global level for all UDP or UDP6 sockets using the following sysctl(7) variables:
net.inet.udp.rfc6056.selected and net.inet6.udp6.rfc6056.selected respectively.
Options at the IP transport level may be used with UDP; see ip(4) or ip6(4).
DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
[EISCONN] when trying to establish a connection on a socket which already has one, or when trying to send a datagram with the destina-
tion address specified and the socket is already connected;
[ENOTCONN] when trying to send a datagram, but no destination address is specified, and the socket hasn't been connected;
[ENOBUFS] when the system runs out of memory for an internal data structure;
[EADDRINUSE] when an attempt is made to create a socket with a port which has already been allocated;
[EADDRNOTAVAIL] when an attempt is made to create a socket with a network address for which no network interface exists.
SEE ALSO getsockopt(2), recv(2), send(2), socket(2), inet(4), inet6(4), intro(4), ip(4), ip6(4), rfc6056(7), sysctl(7)
User Datagram Protocol, RFC, 768, August 28, 1980.
Requirements for Internet Hosts -- Communication Layers, RFC, 1122, October 1989.
HISTORY
The udp protocol appeared in 4.2BSD.
BSD September 24, 2011 BSD