---
name: "udp"
section: "3tnm"
platform: "linux"
package: "scotty"
version: "4:00-02-21-2"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/udp/3tnm"
---

# udp(3tnm)

Send and receive UDP datagrams.

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## NAME

Tnm::udp - Send and receive UDP datagrams.

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## DESCRIPTION

The Tnm::udp command allows to send and receive datagrams using the User Datagram Protocol (UDP) (RFC 768).

## UDP COMMAND

- **Tnm::udp open \[*port*\]**

  The **Tnm::udp open** command opens a UDP datagram socket and returns a handle. The socket is bound to a given *port* number or name. An unused port number is used if the *port* argument is missing.

- **Tnm::udp connect *host* *port***

  The **Tnm::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 Tnm::udp send command on a connected UDP socket. The command returns a udp handle.

- **Tnm::udp send *handle* \[*host port*\] *message***

  The **Tnm::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.

- **Tnm::udp receive *handle***

  The **Tnm::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 Tnm::udp bind command.

- **Tnm::udp close *handle***

  The **Tnm::udp close** command closes the UDP socket associated with *handle*.

- **Tnm::udp bind *handle* readable \[*script*\]**

  - **Tnm::udp bind *handle* writable \[*script*\]**

  The **Tnm::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 Tnm::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.

- **Tnm::udp info \[*handle*\]**

  The **Tnm::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)](/scotty/1.md), Tnm(n), [Tcl(n)](/Tcl/n.md)

## AUTHORS

Juergen Schoenwaelder \<schoenw@ibr.cs.tu-bs.de\>\