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AT Commands

Introduction

AT commands are used for controlling modem, GSM, and many other types of communication equipment that come with a serial port. CommFront’s device servers / serial to Ethernet converters use AT commands for querying or setting parameters such as COM port and IP parameters. 

AT Command Syntax

“AT” stands for “attention”, and it must be used at the beginning of each command line. The AT command must be terminated with a <CR> code (HEX code: 0D). AT commands are usually responded to by the device, and the response looks something like: “AT+COMMAND<CR><CR><LF><response><CR><LF>”. Throughout this document, only the responses are presented. “<CR><LF>” is omitted intentionally.

Command syntax

Query command:

AT+COMMAND<CR>

Set command:

AT+COMMAND=<parameter1,parameter2,…><CR>

Response syntax

Query command:

+OK=<parameter1,parameter2,…>

Set command:

+OK

Error:
+ERR=<number>

Error codes

Error Code Description
1 Invalid format
2 Invalid command
3 Invalid operator
4 Invalid parameter
5 Invalid operation


Software Tools and Examples

The example below demonstrates how CommFront’s device servers / serial to Ethernet converters use AT commands for querying and setting network parameters.

  • CommFront’s 232Analyzer software provides an easy and fast way for sending AT commands (download link: https://www.commfront.com/pages/downloads). 
  • Run the 232Analyzer software and set the COM port settings to 115.2Kbps, 8, N, 1. Then select “ASCII” for both TX and RX data formats.
    AT Commands: COM settings
  • To enter AT Command mode, first send the ASCII code: +++
    Enter AT Commands
  • The device server responds with an ASCII code: a
  • Send the second ASCII code within 3 seconds: a
    Enter AT Commands - Response
  • The device server responds with an ASCII code and it now enters into “AT Command” mode: +ok
  • Query current network settings: AT+WANN<CR>
    AT Command: Query
  • The device server responds with the current network settings: +OK=STATIC,192.168.1.201,255.255.255.0,192.168.1.254
  • Change current network settings to the same sub network as your PC’s, e.g.: AT+WANN=STATIC,172.16.0.100,255.255.255.0,172.16.0.1
    <CR>
    AT Command: Change settings
  • The device server responds with a confirmation code: +OK
  • Restart the device server for the new settings to take effect: AT+Z<CR>

    AT Command: Settings
  • The device server restarts and exits the “AT command” mode.

AT Commands Set

  • Switch from data mode to AT command mode
    • Command Response

    +++

    a

    Send next command within 3 seconds

     

    a

    +ok

     

    Enter AT Command mode

     

    • Switch from AT command mode to data mode
    Command Response

    AT+ENTM<CR>

    +OK

     

    Exit AT Command mode

     

    • Restart the device
    Command Response

    AT+Z<CR>

    +OK

     

    Restart the device and exit AT Command mode

     

    • Restore factory settings
    Command Response

    AT+RELD<CR>

    +OK

     

    Require device restart for factory settings to take effect

     

    • Query MAC address
    Command Response

    AT+MAC<CR>

    +OK=<MAC>

     

    Example: +OK=D8C561010001

     

    • Query or set Network parameters
    Command Response

    AT+WANN<CR>

    +OK=<type,IP_address,subnet_mask,gateway>

    AT+WANN=<type,IP_address,subnet_mask,gateway><CR>

    +OK

    Example: AT+WANN=STATIC,
    192.168.1.201,255.255.255.0,192.168.1.254<CR>

     

     

    • Query or set DNS address
    Command Response

    AT+DNS<CR>

    +OK=<address>

    AT+DNS=<address><CR>

    +OK

    Example: AT+DNS=8.8.8.8<CR>

     

     

    • Query or set COM port parameters
    Command Response

    AT+UART<CR>

    +OK=<baud_rate,data_bit,stop_
    bit,parity,flowctrl>

    AT+UART=<baud_rate,data_bit,stop_
    bit,parity,flow_ctrl><CR>

    +OK

    Baud rate: 9600,19200,38400,57600,
    115200,128000,256000
    Data bit: 7,8

    Stop bit: 1,2

    Parity: None, Even, Odd, Mask, Space

    Flow Ctrl: No Hardware Control (NFC),

    Hardware Control (FCH)

     

    Example: AT+UART=115200,8,1,NONE,NFC<CR>

     

     

    • Query or set Socket parameters
    Command Response

    AT+SOCK<CR>

    +OK=<socket,IP,port>

    AT+SOCK=<socket,IP,port><CR>

    +OK

    Socket:
    TCPS – TCP Server

    TCPC – TCP Client

    UDPS – UDP Server

    UDPC – UDP Client

    HTPC – Httpd Client

    IP: Remote IP address or domain

    Port: Local port (for server) or Remote port (for client)

     

    Example 1: AT+SOCK=TCPS,
    192.168.1.211,502<CR>

    Example 2: AT+SOCK=TCPC,
    192.168.1.211,20000<CR>

     

     

    • Query TCP connection status
    Command Response

    AT+SOCKLK<CR>

    +OK=<status>

    Status:

    CONNECT – TCP connection has been established

    DISCONNECT – TCP connection has not been established

     

     

    Example: +OK=CONNECT
    • Query or set Local port
    Command Response

    AT+SOCKPORT<CR>

    +OK=<number>

    AT+SOCKPORT=<number><CR>

    +OK

    Number:

    0 – Random

    1-65535 – Local port

     

    Example: AT+SOCKPORT=502<CR>

     

     

    • Query Production time
    Command Response

    AT+PDTIME<CR>

    +OK=<time>

     

    Example: +OK=2021-01-01 15:43:11

     

    • Query or set Registry packet type
    Command Response

    AT+REGEN<CR>

    +OK=<type>

    AT+REGEN=<type><CR>

    +OK

    Type:

    OFF: No registry packet is used

    MAC – Use MAC address as registry packet

    USR – Use user-defined packet

    CLOUD – Use cloud packet

     

    Example: AT+REGEN=MAC<CR>

     

     

    • Query or set When to send registry packet
    Command Response

    AT+REGTCP<CR>

    +OK=<type>

    AT+REGTCP=<type><CR>

    +OK

    Type:

    FIRST – Send together with connection string

    EVERY – Send together with data string

    ALL – Send together with connection and data string

     

    Example: AT+REGTCP=FIRST<CR>

     

     

    • Query or set Device ID and cloud key for cloud connection
    Command Response

    AT+REGCLOUD<CR>

    +OK=<deviceID,cloudKey>

    AT+REGCLOUD=<deviceID,cloudKey><CR>

    +OK

    Device ID – Device ID for cloud connection

    Cloud Key – Cloud key for cloud connection

     

    Example: AT+REGCLOUD=00000001,0001<CR>

     

     

    • Query or set User-defined registry packet
    Command Response

    AT+REGUSR<CR>

    +OK=<data>

    AT+REGUSR=<data><CR>

    +OK

    Data: ASCII codes (up to 40 bytes)

     

    Example: AT+REGUSR=www.commfront.com
    <CR>

     

     

    • Query or set HTTP request method
    Command Response

    AT+HTPTP<CR>

    +OK=<method>

    AT+HTPTP=<method><CR>

    +OK

    Method:

    GET – Use GET method for HTTP request

    POST – Use POST method for HTTP request

     

    Example: AT+HTPTP=GET<CR>

     

     

    • Query or set HTTP request URL
    Command Response

    AT+HTPURL<CR>

    +OK=<url>

    AT+HTPURL=<url><CR>

    +OK

    URL: Less than 100 characters

     

    Example: AT+HTPURL=/1.php<CR>

     

     

    • Query or set HTTP request header
    Command Response

    AT+HTPHEAD<CR>

    +OK=<data>

    AT+HTPHEAD=<data><CR>

    +OK

    Header: Less than 200 characters

     

    Example: AT+HTPHEAD=User_Agent: Mozila/4.0<CR>

     

     

    • Enable or disable Remove HTTP request header
    Command Response

    AT+HTPCHD<CR>

    +OK=<status>

    AT+HTPCHD=<status><CR>

    +OK

    Status:

    ON – Remove HTTP request header

    OFF – Keep HTTP request header

     

    Example: AT+HTPCHD=OFF<CR>

     

     


     

    • Enable or disable Heartbeat function
    Command Response

    AT+HEARTEN<CR>

    +OK=<status>

    AT+HEARTEN=<status><CR>

    +OK

    Status:
    ON – Enable heartbeat function

    OFF – Disable heartbeat function

     

    Example: AT+HEARTEN=ON<CR>

     

     

    • Query or set Direction to send heartbeat packet
    Command Response

    AT+HEARTTP<CR>

    +OK=<type>

    AT+HEARTTP=<type><CR>

    +OK

    Type:

    COM – Send heartbeat packet to COM port

    NET – Send heartbeat packet to network port

     

    Example: AT+HEARTTP=NET<CR>

     

     

    • Query or set Heartbeat interval
    Command Response

    AT+HEARTTM<CR>

    +OK=<time>

    AT+HEARTTM=<time><CR>

    +OK

    Time: 1 – 65535s

     

    Example: AT+HEARTTM=30<CR>

     

     

    • Query or set Heartbeat packet
    Command Response

    AT+HEARTDT<CR>

    +OK=<data>

    AT+HEARTDT=<data><CR>

    +OK

    Data: ASCII codes (up to 40 bytes)

     

    Example: AT+HEARTDT=www.commfront.com<CR>

     

     

    • Enable or disable Restart after 30 times of unsuccessful connection attempts (TCP client mode)
    Command Response

    AT+CLIENTRST<CR>

    +OK=<status>

    AT+CLIENTRST=<status><CR>

    +OK

    Status:

    ON – Enable restart after 30 times of unsuccessful TCP connection attempts

    OFF – Disable restart after 30 times of unsuccessful TCP connection attempts

     

    Example: AT+CLIENTRST=ON<CR>

     

     


     

    • Enable or disable Link function
    Command Response

    AT+SCSLINK<CR>

    +OK=<status>

    AT+SCSLINK=<status><CR>

    +OK

    Status:

    ON – Socket link function is ON

    OFF – Socket link function is OFF

     

    Example: AT+SCSLINK=ON<CR>

     

     

    • Enable or disable Index function (TCP server mode)
    Command Response

    AT+INDEXEN<CR>

    +OK=<status>

    AT+INDEXEN=<status><CR>

    +OK

    Status:

    ON – Enable index function

    OFF – Disable index function

     

    Example: AT+INDEXEN=ON<CR>

     

     

    • Enable or disable RFC2217
    Command Response

    AT+RFCEN<CR>

    +OK=<status>

    AT+RFCEN=<status><CR>

    +OK

    Status:

    ON – Enable RFC2217

    OFF – Disable RFC2217

     

    Example: AT+RFCEN=ON<CR>

     

     

    • Enable or disable Short connection function
    Command Response

    AT+SOCKSL<CR>

    +OK=<status>

    AT+SOCKSL=<status><CR>

    +OK

    Status:

    ON – Enable short connection function

    OFF – Disable short connection function

     

    Example: AT+SOCKSL=ON<CR>

     

     

    • Query or set Short connection timeout
    Command Response

    AT+SHORTO<CR>

    +OK=<time>

    AT+SHORTO=<time><CR>

    +OK

    Time: 2-255s

     

    Example: AT+SHORTO=3<CR>

     

     


     

    • Query or set Server actions when maximum number of client connections is reached
    Command Response

    AT+TCPSE<CR>

    +OK=<action>

    AT+TCPSE=<action><CR>

    +OK

    Status:

    KEEP – Keep old connection

    KICK – Disable old connection and allow new connection

     

    Example: AT+TCPSE=KEEP<CR>

     

     

    • Enable or disable Clear serial buffer upon TCP/IP connection
    Command Response

    AT+UARTCLBUF<CR>

    +OK=<status>

    AT+UARTCLBUF=<status><CR>

    +OK

    Status:

    ON – Enable Clear serial buffer upon TCP/IP connection

    OFF – Disable Clear serial buffer upon TCP/IP connection

     

    Example: AT+UARTCLBUF=ON<CR>

     

     

    • Enable or disable Modbus RTU to Modbus TCP conversion
    Command Response

    AT+MODTCP<CR>

    +OK=<status>

    AT+MODTCP=<status><CR>

    +OK

    Status:

    ON – Enable Modbus RTU to Modbus TCP conversion

    OFF – Disable Modbus RTU to Modbus TCP conversion

     

    Example: AT+MODTCP=ON<CR>

     

     

    • Query or set Device name
    Command Response

    AT+MID<CR>

    +OK=<name>

    AT+MID=<name><CR>

    +OK

    Name: Up to 14 characters

     

    Example: AT+MID=DVS-485-2<CR>

     

     

    • Query or set Web port
    Command Response

    AT+WEBPORT<CR>

    +OK=<port>

    AT+WEBPORT=<port><CR>

    +OK

    Example: AT+WEBPORT=80<CR>

     

     


     

    • Query or set User_name and password
    Command Response

    AT+WEBU<CR>

    +OK=<username,password>

    AT+WEBU=<username,password><CR>

    +OK

    Example: AT+WEBU=user,password<CR>

     

     

    • Query Firmware version
    Command Response

    AT+VER<CR>

    +OK=<ver>

     

    • Query or set Maximum number or client connections (server mode)
    Command Response

    AT+MAXSK<CR>

    +OK=<number>

    AT+MAXSK=<number><CR>

    +OK

    Number: 1 to 8

     

    Example: AT+MAXSK=8<CR>

     

     

    • Query or set No data auto-restart timeout
    Command Response

    AT+RSTIM<CR>

    +OK=<time>

    AT+RSTIM=<time><CR>

    +OK

    Time:

    0 – No auto-restart

    60-65535s – Auto-restart timeout if no data received from serial or network port

     

    Example: AT+RSTIM=3600<CR>

     

     

    • Get Help information
    Command Response

    AT+H<CR>

    +OK=<info>