SARA-R4/N4 series - AT Commands Manual
UBX-17003787 - R09
18 Internet protocol transport layer
Page 180 of 307
18 Internet protocol transport layer
18.1 Introduction
SARA-R4 / SARA-N4
Before using TCP/IP services, a connection profile must be defined and activated. The sockets can be
managed independently and simultaneously over the same bearer (either PSD or CSD). AT commands for
both reading and writing data on sockets are provided and the URC notifies the external application of
incoming data and transmission result, no need for polling.
SARA-R4 / SARA-N4
When these commands report an error result code which is not a +CME ERROR, the error code can be
queried using the
(specifying the socket ID and with <param_id>=1) AT commands.
The maximum number of sockets that can be managed are 7.
SARA-R4 / SARA-N4
The maximum number of secure sockets that can be managed is 4.
SARA-R4 / SARA-N4
No need to establish a PSD connection explicitly. This device automatically establishes a PSD connection
as part of the network registration and attach procedure.
The UDP protocol has not any flow control mechanism and packets might be lost in the following
scenarios:
• No network signal is available
• Unreliable radio interface (e.g. mobility in GPRS, where cell reselections can lead to data loss, that can
be contrasted with the usage of LLC ack reliability QoS parameter
Some network operators close dynamic NATs after few minutes if there is no activity on the connection
(no data transfer in the period). To solve this problem enable the TCP keep alive options with 1 minute
delay (see the
AT command).
When both TCP and UDP socket are used at the same time at the maximum throughput (downlink and
uplink at the maximum allowed baud rate) it is possible to lose some incoming UDP packets due to internal
buffer limitation. A possible workaround is provided as follows:
• If it is possible, adopt an application layer UDP acknowledge system
18.2 IPv4/IPv6 addressing
18.2.1 Introduction
The section describes the IP addressing formats and IP address rules used by TCP/IP UDP/IP enabled
applications.
18.2.2 IPv4
Format:
• 32 bits long in dot-decimal notation (without leading 0 notation).
• All the decimal numbers must be in range 0-255.
• The dot-octal notation is not supported.
• The dot-hexadecimal notation is not supported.
Examples:
IPv4 address
Remarks
254.254.254.254
Valid address
010.228.76.34
Invalid address; first decimal number prefixed with a leading zero
257.228.76.34
Invalid address; first decimal number greater than 255
0010.0344.0114.0042
Invalid address; dot-octal notation; decimals given as octal numbers
