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udp(4) [freebsd man page]

UDP(4)							   BSD Kernel Interfaces Manual 						    UDP(4)

udp -- Internet User Datagram Protocol SYNOPSIS
#include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> int socket(AF_INET, 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. Options at the IP transport level may be used with UDP; see ip(4). MIB VARIABLES
The udp protocol implements a number of variables in the net.inet branch of the sysctl(3) MIB. UDPCTL_CHECKSUM (udp.checksum) Enable udp checksums (enabled by default). UDPCTL_MAXDGRAM (udp.maxdgram) Maximum outgoing UDP datagram size UDPCTL_RECVSPACE (udp.recvspace) Maximum space for incoming UDP datagrams udp.log_in_vain For all udp datagrams, to ports on which there is no socket listening, log the connection attempt (disabled by default). udp.blackhole When a datagram is received on a port where there is no socket listening, do not return an ICMP port unreachable message. (Disabled by default. See blackhole(4).) ERRORS
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 desti- nation address specified and the socket is already connected; [ENOTCONN] when trying to send a datagram, but no destination address is specified, and the socket has not 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), blackhole(4), inet(4), intro(4), ip(4) HISTORY
The udp protocol appeared in 4.2BSD. BSD
June 5, 1993 BSD

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udp(n)								 Tnm Tcl Extension							    udp(n)


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 <> Tnm udp(n)
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