TCP and UDP AT commands

This page describes TCP- and UDP-related AT commands. When native TLS is used, you must store the credentials using the AT#XCMNG AT command.

For more information on the networking services, see the Zephyr Network APIs.

TCP server #XTCPSVR

The #XTCPSVR command allows you to start and stop the TCP/TLS server.

Set command

The set command allows you to start and stop the TCP/TLS server.

Syntax

#XTCPSVR=<op>[<port>[,<sec_tag>]]

  • The <op> parameter can accept one of the following values:

    • 0 - Stop the server.

    • 1 - Start the server using IP protocol family version 4.

    • 2 - Start the server using IP protocol family version 6.

  • The <port> parameter is an unsigned 16-bit integer (0 - 65535). It represents the TCP service port. It is mandatory to set it when starting the server.

  • The <sec_tag> parameter is an integer. If it is given, a TLS server will be started. It indicates to the modem the credential of the security tag used for establishing a secure connection. Can only be used when the overlay-native_tls.conf configuration file is used.

Response syntax

#XTCPSVR: <handle>,"started"

#XTCPSVR: <error>,"not started"

  • The <handle> value is an integer. When positive, it indicates the handle of the successfully opened listening socket.

  • The <error> value is an integer. It represents the error value according to the standard POSIX errno.

Unsolicited notification

#XTCPSVR: "<peer ip>","connected"

This is emitted when a new connection has been created to the server.

  • The <peer_ip> value is the IPv4 or IPv6 address of the peer.

#XTCPSVR: <error>,"disconnected"

This is emitted when the client has been disconnected.

  • The <error> value is an integer. It is either 0 when the client is disconnected normally, or an -errno code.

Example

AT#XTCPSVR=1,3442,600
#XTCPSVR: 2,"started"
#XTCPSVR: "123.456.789.123","connected"
#XTCPSVR: 0,"disconnected"
OK

Read command

The read command allows you to check the TCP server settings.

Syntax

#XTCPSVR?

Response syntax

#XTCPSVR: <listen_socket_handle>,<income_socket_handle>,<family>

  • The <xxx_socket_handle> value is an integer. When positive, it indicates that the socket opened successfully. When negative, it indicates that the socket failed to open or that there is no incoming connection.

  • The <family> value is an integer.

    • 1 - IP protocol family version 4.

    • 2 - IP protocol family version 6.

Examples

AT#XTCPSVR?
#XTCPSVR: 1,2,1
OK

Test command

The test command tests the existence of the command and provides information about the type of its subparameters.

Syntax

#XTCPSVR=?

Response syntax

#XTCPSVR: <list of ops>,<port>,<sec_tag>

Examples

AT#XTCPSVR=?
#XTCPSVR: (0,1,2),<port>,<sec_tag>
OK

TCP/TLS client #XTCPCLI

The #XTCPCLI command allows you to create a TCP/TLS client and to connect to a server.

Set command

The set command allows you to create a TCP/TLS client and to connect to a server.

Syntax

#XTCPCLI=<op>[,<url>,<port>[,sec_tag[,peer_verify[,hostname_verify]]]]

  • The <op> parameter can accept one of the following values:

    • 0 - Disconnect.

    • 1 - Connect to the server for IP protocol family version 4.

    • 2 - Connect to the server for IP protocol family version 6.

  • The <url> parameter is a string. It indicates the hostname or the IP address to connect to. Its maximum size is 128 bytes. When the parameter is an IP address, it supports both IPv4 and IPv6.

  • The <port> parameter is an unsigned 16-bit integer (0 - 65535). It represents the TCP/TLS service port on the remote server.

  • The <sec_tag> parameter is an integer. If it is given, a TLS client will be started. It indicates to the modem the credential of the security tag used for establishing a secure connection.

  • The <peer_verify> parameter accepts the following values:

    • 0 - None. Do not authenticate the peer.

    • 1 - Optional. Optionally authenticate the peer.

    • 2 - Required (default). Authenticate the peer.

  • The <hostname_verify> parameter accepts the following values:

    • 0 - Do not verify the hostname against the received certificate.

    • 1 - Verify the hostname against the received certificate (default).

See nRF socket options peer_verify and tls_hostname for more information on <peer_verify> and <hostname_verify>.

Response syntax

#XTCPCLI: <handle>,"connected"

#XTCPCLI: <error>,"not connected"

  • The <handle> value is an integer. When positive, it indicates the handle of the successfully opened socket.

  • The <error> value is an integer. It is either an errno code or one of the dns_resolve_status values defined in zephyr/net/dns_resolve.h.

Examples

AT#XTCPCLI=1,"remote.ip",1234
#XTCPCLI: 2,"connected"
OK

Read command

The read command allows you to verify the status of the connection.

Syntax

#XTCPCLI?

Response syntax

#XTCPCLI: <handle>,<family>

  • The <handle> value is an integer. When positive, it indicates the handle of the successfully opened socket. When negative, it indicates that the client socket failed to open.

  • The <family> value is an integer.

    • 1 - IP protocol family version 4.

    • 2 - IP protocol family version 6.

Test command

The test command tests the existence of the command and provides information about the type of its subparameters.

Syntax

#XTCPCLI=?

Response syntax

#XTCPCLI: <list of ops>,<url>,<port>,<sec_tag>,<peer_verify>,<hostname_verify>

Examples

AT#XTCPCLI=?
#XTCPCLI: (0,1,2),<url>,<port>,<sec_tag>,<peer_verify>,<hostname_verify>
OK

TCP send data #XTCPSEND

The #XTCPSEND command allows you to send the data over the connection.

Set command

The set command allows you to send the data over the connection. When used from a TCP/TLS client, it sends the data to the remote TCP server When used from a TCP server, it sends data to the remote TCP client

Syntax

#XTCPSEND[=<data>]

  • The <data> parameter is a string that contains the data to be sent. The maximum size of the data is 1024 bytes. When the parameter is not specified, SLM enters slm_data_mode.

Response syntax

#XTCPSEND: <size>

  • The <size> value is an integer. It represents the actual number of the bytes sent.

Examples

AT#XTCPSEND="Test TLS client"
#XTCPSEND: 15
OK

Read command

The read command is not supported.

Test command

The test command is not supported.

TCP hang up #XTCPHANGUP

The #XTCPHANGUP command allows you to disconnect an incoming connection.

Set command

The set command allows you to disconnect an incoming connection. This function is reserved to TCP server role by its nature.

Syntax

#XTCPHANGUP=<handle>

  • The <handle> parameter is an integer. Refer to #XTCPSVR? command for the <income_socket_handle>.

Response syntax

#XTCPSVR: <error>,"disconnected"

This is emitted when the client has been disconnected.

  • The <error> value is an integer. It is either 0 when the client is disconnected normally, or an -errno code.

Examples

AT#XTCPSVR?
#XTCPSVR: 1,2,1
OK
AT#XTCPHANGUP=2
#XTCPSVR: 0,"disconnected"
OK

Read command

The read command is not supported.

Test command

The test command tests the existence of the command and provides information about the type of its subparameters.

Syntax

#TCPHANGUP=?

Response syntax

#TCPHANGUP: <handle>

Examples

AT#TCPHANGUP=?
#TCPHANGUP: <handle>
OK

TCP receive data

#XTCPDATA: <size>
<data>

  • The <size> parameter is an integer that indicates the size of the received data. This notification comes only when SLM is not operating in data mode.

  • The <data> parameter is a string that contains the data received.

UDP server #XUDPSVR

The #XUDPSVR command allows you to start and stop the UDP server.

Note

DTLS server functionality is not supported by nRF91 Series devices.

Set command

The set command allows you to start and stop the UDP server.

Syntax

#XUDPSVR=<op>[,<port>]

  • The <op> parameter can accept one of the following values:

    • 0 - Stop the server.

    • 1 - Start the server for IP protocol family version 4.

    • 2 - Start the server for IP protocol family version 6.

  • The <port> parameter is an unsigned 16-bit integer (0 - 65535). It represents the UDP service port. It is mandatory for starting the server.

Response syntax

#XUDPSVR: <handle>,"started"

  • The <handle> value is an integer. It indicates the handle of the successfully opened listening socket.

Examples

AT#XUDPSVR=1,3442
#XUDPSVR: 2,"started"
OK

Read command

The read command allows you to check the current value of the subparameters.

Syntax

#XUDPSVR?

Response syntax

#XUDPSVR: <handle>,<family>

  • The <handle> value is an integer. When positive, it indicates the handle of the successfully opened socket. When negative, it indicates that it failed to open.

  • The <family> value is an integer.

    • 1 - IP protocol family version 4.

    • 2 - IP protocol family version 6.

Test command

The test command tests the existence of the command and provides information about the type of its subparameters.

Syntax

#XUDPSVR=?

Response syntax

#XUDPSVR: <list of ops>,<port>

Examples

AT#XUDPSVR=?
#XUDPSVR: (0,1,2),<port>
OK

UDP/DTLS client #XUDPCLI

The #XUDPCLI command allows you to create a UDP/DTLS client and to connect to a server.

Note

The UDP/DTLS client always works in a connection-oriented way.

Set command

The set command allows you to create a UDP/DTLS client and connect to a server.

Syntax

#XUDPCLI=<op>[,<url>,<port>[,<sec_tag>[,<use_dtls_cid>[,peer_verify[,hostname_verify]]]]]

  • The <op> parameter can accept one of the following values:

    • 0 - Disconnect.

    • 1 - Connect to the server for IP protocol family version 4.

    • 2 - Connect to the server for IP protocol family version 6.

  • The <url> parameter is a string. It indicates the hostname or the IP address to connect to. Its maximum size can be 128 bytes. When the parameter is an IP address, it supports both IPv4 and IPv6.

  • The <port> parameter is an unsigned 16-bit integer (0 - 65535). It represents the UDP/DTLS service port on the remote server.

  • The <sec_tag> parameter is an integer. If it is given, a DTLS client will be started. It indicates to the modem the credential of the security tag used for establishing a secure connection.

  • The <use_dtls_cid> parameter is an integer. It indicates whether to use DTLS’s connection identifier. This parameter is only supported with modem firmware 1.3.5 and newer. See Secure socket options #XSSOCKETOPT for more details regarding the allowed values. The command will fail (with <error> equal to -134 (-ENOTSUP) if the requested connection identifier is not accepted by the server.

  • The <peer_verify> parameter accepts the following values:

    • 0 - None. Do not authenticate the peer.

    • 1 - Optional. Optionally authenticate the peer.

    • 2 - Required (default). Authenticate the peer.

  • The <hostname_verify> parameter accepts the following values:

    • 0 - Do not verify the hostname against the received certificate.

    • 1 - Verify the hostname against the received certificate (default).

See nRF socket options peer_verify and tls_hostname for more information on <peer_verify> and <hostname_verify>.

Response syntax

#XUDPCLI: <handle>,"connected"

#XUDPCLI: <error>,"not connected"

  • The <handle> value is an integer. When positive, it indicates the handle of the successfully opened socket.

  • The <error> value is an integer. It is either an errno code or one of the dns_resolve_status values defined in zephyr/net/dns_resolve.h.

Examples

AT#XUDPCLI=1,"remote.host",2442
#XUDPCLI: 2,"connected"
OK

Read command

The read command allows you to check the current value of the subparameters.

Syntax

#XUDPCLI?

Response syntax

#XUDPCLI: <handle>,<family>

  • The <handle> value is an integer. When positive, it indicates the handle of the successfully opened socket. When negative, it indicates that it failed to open.

  • The <family> value is an integer.

    • 1 - IP protocol family version 4.

    • 2 - IP protocol family version 6.

Test command

The test command tests the existence of the command and provides information about the type of its subparameters.

Syntax

#XUDPCLI: <list of ops>,<url>,<port>,<sec_tag>,<use_dtls_cid>,<peer_verify>,<hostname_verify>

Examples

AT#XUDPCLI=?
#XUDPCLI: (0,1,2),<url>,<port>,<sec_tag>,<use_dtls_cid>,<peer_verify>,<tls_hostname_verify>
OK

UDP send data #XUDPSEND

The #XUDPSEND command allows you to send data over the connection.

Set command

The set command allows you to send data over the connection.

Syntax

#XUDPSEND[=<data>]

  • The <data> parameter is a string that contains the data to be sent. The maximum size of the data is 1024 bytes. When the parameter is not specified, SLM enters slm_data_mode.

Response syntax

#XUDPSEND: <size>

  • The <size> value is an integer. It indicates the actual number of bytes sent.

Examples

AT#XUDPSEND="Test UDP by hostname"
#XUDPSEND: 20
OK

Read command

The read command is not supported.

Test command

The test command is not supported.

UDP receive data

#XUDPDATA: <size>
<data>

  • The <size> parameter is an integer that indicates the size of the received data. This notification comes only when SLM is not operating in data mode.

  • The <data> parameter is a string that contains the data received.