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Programmer Guide(Eng)


This page provides detailed information about AT commands set and how to use the Configuration tool, which retrieves and sets all configurations of WIZ550S2E via Ethernet. Users can change any value of the WIZ550S2E and communicate with the peer system through TCP(or UDP) socket by sending AT commands.

WIZ550S2E AT Command Set

This section provides a list of WIZ550S2E AT commands and their functions. Users can input commands and parameters through USART line.

Enter/Exit Command Mode

The command mode is entered by sending the "Trigger Code" (default 2B 2B 2B in Hex) to the serial port of the WIZ550S2E module. This three byte Trigger Code needs to be sent without any character before and after the three byte = also without CR or LF for 500ms time.
The command mode is closed by sending "AT+MDATA/r/n" The Trigger Code can be en/disabled and also changed with the config tool.

The three byte Trigger Code need to be isolated = without CR(0x0D), LF(0x0A)

Every command starts with “AT”. Any other initial character will cause an error in return. Commands and parameters are all ASCII characters, i.e. when you input 'AT+NSTAT', you should input ASCII characters 'A', 'T', '+', 'N', 'S', 'T', 'A', 'T' and 'Enter Key' which is CR, LF (0x0d, 0x0A).

All commands should be terminated with CR(0x0D), LF(0x0A)

Some parameters are mandatory and others are optional. Parameters must be entered in the order of format column given by the command tables. Although the optional parameter is not used, the comma delimiters ',' must still be included in the command. In most cases, valid commands return the character [S] and invalid inputs return [F]. The possible responses sent from WIZ550S2E to the user are described as Responses. Below are examples of user input. As you can see, WIZ550S2E return “\r\n” back instead of “\r”, which means user (host system) always handle '\r\n' as the only delimiter.

Input by UserAT\r\n (0x61 0x74 0x0d 0x0a)
Output from WIZ550S2E[S]\r\n (0x5b 0x53 0x5d 0x0d 0x0a)


Response Format


  • (Type): Type of response. It can be one of S, D, F, W, R and V.

  • (Id): Socket Identifier. This is the mandatory in Async mode.

  • (Param1) ~ (Param6): ): These are included in case of commands retrieving module's setting value.

  • ↓: This means 'Enter' key as delimiter and CR, LF(0x0d, 0x0a) are its real value.

  • (Data): When huge data are needed, 'Data' will be followed in case of Type of response, D and R.

Responses are listed below.

Success Response[S,(Id),(Param1),(Param2),(Param3),(Param4),(Param5),(Param6)]↓
Command Request Success, outputs with param when it's needed.
Success Dump Response[D,(Id),(Size)]↓(Data)↓
Command Request Success, Outputs large data include 'Enter key' value.
Fail Response[F,(Id),(ErrorCode),(ErrorParam)]↓
Command Request Fail, outputs with param when it's needed.
Wait Response[W,(Id)]↓
Command is started with ID in Async mode.
Data Receive Response[R,(SockId),(ReceivedSize),(SrcIP),(SrcPort)]↓(Data)↓
Outputs the received data.
Event Response[V,(Id),(EventCode)]↓
Event occurred.
  • (Id): 0 - System ID or 0~n - Socket Number
  • (Size): Byte size of the output data
  • (ErrorCode): Error Code
  • (ErrorParam): Value of description for Error Code
  • (SockId): Socket Identifier of the socket which received data
  • (ReceivedSize): Byte size of received data
  • (SrcIP): Sender's IP address. This is mandatory in case of UDP & TCP Client. In case of TCP Server this is omitted.
  • (SrcPort): Sender socket's port number. This is mandatory in case of UDP & TCP Client.In case of TCP Server this is omitted.
  • (EventCode): Indication of which event happened.

Error Code

General Error Code
CodeError NameDescription
0ERR_UndefinedUndefined Error
1ERR_WrongOperatorWrong Operator
2ERR_WrongCommandSignWrong Command Sign
3ERR_WrongArgumentsWrong Arguments
4ERR_OurofRangeParameter is out of Range
5ERR_FuncDisabledThis function is disabled
6ERR_NotAllowedNot Allowed
7ERR_CommandBusyCommand Busy
8ERR_CommandTimeoutCommand Timeout
Socket Error Code
CodeError NameDescription
10ERR_SockNotAvailSocket Not Available
11ERR_SockClosedSocket Closed
12ERR_SockPortNumNotAvailPort Not Available
13ERR_SockNotConnectedNot Connected
14ERR_SockWrongAddrWrong Address
15ERR_SockDataNotAvailableData Not Available
Other Error Code
CodeError NameDescription
20ERR_NoFreeMemNo Free Memory

Event Code

Socket Event Code
CodeSocket Event NameDescription
0EVENT_SockConnectedConnected. Socket transition from Listen state to established state
1EVENT_SockDisconnectedDisconnected. Socket transition from established state to disconnected state
2EVENT_SockClosedClosed. Socket transition to closed state
3EVENT_SockDataRcvdData Received. The corresponding socket received data from its peer

Network Commands

CommandProp.Input ParameterResponse
AT+NSETNone or ?[S,,S,(IP),(SN),(GW),(DNS)]
AT+NSTATNone or ?[S,,S/D,(IP),(SN),(GW),(DNS)]
AT+NMACNone or ?[S,,(MAC)]
AT+NSOCKNone or ?[D,,(Size)]↓(Data)


  • Format:


  • Meaning: Network Configuration

< DHCP>: Static/DHCP

SDHCP Off, Static

< IP>: IP Address (Optional)
< SN>: Subnet Mask (Optional)
< GW>: Gateway Address (Optional)
< DNS>: DNS Address(Optional)



  • Example 1:



  • Meaning: Get Current Network Setting

Note that < IP>,< SN>,< GW>,< DNS> address of response are not actual addresses, but addresses stored in the memory. So when DHCP is on, they are usually different from actual addresses.



  • Example 2:


  • Meaning: Update Second Parameter

  • Response:



  • Format:



  • Meaning: Display Current Network Status

  • Response:


  • Example 1:


  • Meaning: Display Current Network Status

  • Response:




  • Format:



  • Meaning: Get MAC Address

  • Response:


  • Example 1:


  • Meaning: Set MAC Address

  • Response:


  • Example 2:

AT+NMAC\r\n AT+NMAC?\r\n

Meaning: Get MAC Address

  • Response:



  • Format:


  • Meaning: Initialize Socket

< SockType>: Socket Type

STCP Server Socket
CTCP Client Socket
UUDP Socket

< SrcPort>: Local Port Number
< DstIP>: Destination IP Address

  • Response:



  • Example 1:


  • Meaning: Create TCP Client Socket

  • Response:

  • Example 2:


  • Meaning: Create TCP Server Socket

  • Response: [S,,0]


  • Format:


  • Meaning: Close Socket

< SockId>: Socket ID

  • Response:



  • Example 1:


  • Meaning: // Close Socket//

  • Response:



  • Format:


  • Meaning: Send Data

< SockId>: Socket ID

STCP Server Socket
CTCP Client Socket
UUDP Socket

< SrcPort>: Local Port Number
< DstIP>: Destination IP Address
< DstPort>: Destination Port Number

  • Response:



Example 1:


  • Meaning: In TCP Server mode, Destination IP and port are not need.

  • Response:



  • Notice: This feature has been added to v1.0.3 and v1.1.5 has been renamed AT + MMODE.

  • Format:


  • Meaning: Change the network information of the module (automatically saved in EEPROM)

S/C/U/M: Network Mode
S = Server, C = Client, U = UDP, M = Mixed TCP(Server/Client)

  • Response:


  • Example 1: To change the network information of the module to Client, Local Port 5000, Server IP, Remote Port 5000


  • Meaning: Change & save network information of module to client, local port 5000, server IP, remote port 5000

  • Response:


Management Commands

CommandProp.Input ParameterResponse
AT+MSTATNone or ?[S,,(Version)]
AT+MUSARTNone or ?[S,,(BR),(W),(P),(S),(F)]


  • Format:


  • Meaning: Terminal Check

  • Response:






  • Meaning: Get Current Version

  • Response:



  • Format:


  • Meaning: Serial Interface Configuration

< BR>: Baud rate


< W>: Word length

77 bits
88 bits

< P>: Parity bit


< S>: Stop bit

11 bits
22 bits

< F>: Flow Control

  • Response:

[S,,<BR>,( <W>, <P>, <S> ) <F>]

  • Example1:



  • Meaning: Get Serial Interface Information

  • Response:

[S,,<BR>,( <W>, <P>, <S> ) <F>]

  • Example2:


  • Meaning: Set Serial Interface Information

  • Response:



  • Format:


  • Meaning: Reset the module.

  • Response:



  • Format:


  • Meaning: Terminal Check - exit AT Command mode

  • Response:



  • Format:


  • Meaning: Save the setting value.

The values set via AT+MUSART, AT+NSET (except AT+NMAC) are basically only until the module is reset. (In Data Mode, the corresponding setting value is shared. Check through Search in Configuration Tool) In other words, when module is reset, it returns to the value before setting. However, the user can save the set value through the corresponding command (AT+MSAVE) so that the module does not change even if it is reset. That is, it is the same as Setting function in Configuration Tool.

  • Response:


Function Commands

CommandProp.Input ParameterInput Resp.Query Response




  • Meaning: Do DNS Query and then return its result. Using Domain and DNS Server IP what has set via Configuration Tool.

  • Response:

DNS Timeout


Configuration Tool


WIZ550S2E Configuration tool is an application program which is based on java and can be used in most OS platforms including Windows, MAC OS and Linux. Please download .jar file and execute it over Java Virtual Machine.

There are two options on how to run the configuration tool.

  1. Run the jar file from the GUI environment.
    1. The jar file cannot be opened if the jar file is perceived as a compressed file. In this case, modify the setting of the compression software and do not open the jar file in compressed file method.
    2. In case of Linux or Mac, the following must be given permission.
      1. chmod 0755 WIZ550S2E_Configuration_Tool.jar
  2. Enter the following command in the terminal to run the program.
    1. java -jar WIZ550S2E_Configuration_Tool.jar

WIZ550S2E Configuration tool consists four sections

  1. Common Configuration Section
  2. Network Configuration Section
  3. Serial Configuration Section
  4. Option Configuration Section

Common Configurations

The Search function is used to search for all existing WIZnet's WIZ550 series modules on the same LAN. By using UDP broadcast, it finds all modules on the same subnet, and found devices will be listed in the “Serial to Ethernet” tree(Search Window) with its MAC address.


This function is used to apply your configurations.
When you select the MAC address from the “Search Window”, the default value of the module will be displayed. Modify your configurations and click “Setting” button to apply your settings. The module will re-initialize and save the changed configurations. Users can change the configurations by the following steps.

  1. Select the MAC address of the device which you would like to modify in the “Search Window”
  2. Modify the settings according to your needs
  3. Click the “Setting” button and then "Password Input Windows" pop up
  • Default Password is "WIZnet"
  1. Input "Setting Password" and Click "OK" button
  2. The module will be initialized by a re-booting process
  3. To verify your settings, please click ‘Search’ button and view your new settings

F/W Uploading

Firmware will be uploaded through TFTP. Click “F/W Uploading” Button and a popup window will shows as follow.

Server IP : TFTP Server IP

Server Port : TFTP Server Port (TFTP default Port : 69) File Name : Firmware File Name Password : Setting Password

☞ WIZ550S2E Configure tool is not supported TFTP server. So you use TFTP program separately.


This is the function which makes Module reboot. This requires password to reboot.

Factory Reset

All setting value is initialized to factory default, if the “Factory Reset” button is clicked. Factory default values of WIZ550S2E are listed below.

NetworkLocal IP192.168.11.100
:::Local Gateway192.168.11.1
:::Local Subnet255.255.255.0
:::Local Port5000
:::Remote Port5000
:::Working ModeTCP Server
SerialBaud Rate115200
:::Data Bits8
:::Stop Bits1
:::AT Command USEEnable
:::Trigger Code2B/ 2B / 2B
:::Packing Condition Time0
:::Packing Condition Size0
:::Delimeter Length0
:::Delimeter2D / 2D / 2D / 2D
:::Delimeter Appendix0
OptionsModule NameWIZ550S2E
:::Setting PasswordWIZnet
:::Connection PasswordWIZnet
:::DHCP USEDisable
:::DNS USEDisable
:::DNS Server IP8.8.8.8


Close the configuration tool program window.

Search Window

If you click the “Search” button, all MAC addresses on the same subnet will be displayed.

Search Method


Firmware Version

It displays the firmware version.

Network Status

This field shows the current status of network connection.

Connected : This means that TCP connection is established. Disconnected : This measn that TCP connection is disconnected. UDP : This means that UDP mode is used.

Network Configurations


This section is for setting WIZ550S2E mode's network information

IP: WIZ550S2E's IP Address Gateway: WIZ550S2E's Gateway Address Subnet mask: WIZ550S2E's Subnet Mask Host IP: Peer system's IP address which WIZ550S2E connects(or sends) to, when its operating mode is "TCP Client","TCP Mixed" or "UDP".

☞ If you are unclear about your Local IP, Subnet Mask, Gateway information, you have to get this information from your network administrator. If the IP address is not correct, IP collision or network problems may occur.


This section is for setting WIZ550S2E's Port information.

Local port : WIZ550S2E's local port number Remote port : Peer system socket's port number which WIZ550S2E connects(or sends) to , when its operating mode is "TCP Client","TCP Mixed" or "UDP".

Working Mode

The working mode of WIZ550S2E can be divided into TCP Server, TCP Client and TCP Mixed according to the connection establishing method, but UDP processes the data communication without connection establishment.

During TCP server mode, WIZ550S2E operates as the server and waits for the connection trial from the client. WIZ550S2E operates as the client in TCP Client mode and tries to connect to the server’s IP and Port. Mixed mode supports both Server and Client. The communication process of each mode is as below.

TCP server mode communication

During the TCP Server mode, WIZ550S2E waits for the connection request. TCP Server mode can be useful when the monitoring center attempts to connect to the device, while WIZ550S2E is installed, in order to check the status or provide commands. Normally WIZ550S2E is on the waiting status, and if connection request (SYN) from the monitoring center is received, the connection is established (ESTABLISH), and data communication is processed (Data Transaction), and finally connection is closed (FIN). In order to operate this mode, “Device IP”, “Subnet mask”, “Gateway” and “Local port” should be configured first.

For TCP server mode communication, all network configurations including Local IP, Subnet, Gateway and Local port number should be set correctly.

The Data transmission proceeds as below.

  1. The host connects to the WIZ550S2E which is configured as TCP Server mode.
  2. As the connection is established, data can be transmitted in both directions
(host -> WIZ550S2E / WIZ550S2E -> host)

TCP client mode communication

If WIZ550S2E is set as TCP Client, it tries to establish connection to the TCP server. To operate this mode, “Device IP”, “Subnet mask”, “Gateway”, “Remote host”, and “Remote port” should be set. If “Remote host” has a domain name, you should use the “DNS server” field. In TCP Client mode, WIZ550S2E can actively establish a TCP connection to a host computer when power is supplied.

The Data transmission proceeds as below:

  1. As power is supplied, WIZ550S2E board operating as TCP client mode actively establishes a connection to the TCP server.
  2. If the connection is complete, data can be transmitted in both directions
(host -> WIZ550S2E / WIZ550S2E -> host)

TCP Mixed mode Communication

In this mode, WIZ550S2E normally operates as TCP Server and waits for the connection request from the peer. However, if WIZ550S2E receives data from the serial device before connection is established, it changes to the TCP client mode and sends the data to the TCP server IP. Therefore, during TCP mixed mode, the TCP server mode is operated prior to the TCP client mode.

Like TCP Server mode, the TCP Mixed mode is useful in case where the monitoring center attempts to connect to the serial device, while WIZ550S2E is used, to check the device status. In addition to this, if any emergency occurs in the serial device, the module will change to TCP Client mode to establish the connection to the TCP server and deliver the emergency status of the device.

UDP mode Communication

UDP is not a connection oriented protocol but the communication port should be defined well. If UDP mode is selected, the data from serial interface can be defined where to deliver via the “Remote host” and “Remote port.” The WIZ550S2E can also be defined where to receive Ethernet data from via the “Remote host” and “Local port” definition.

If the data destination and source are the same, the two IP addresses will also be the same. Please note that the destination and source are using the same port.



When there is no data transmission, the connection will close automatically after the specified inactivity time. If the default value ‘0’ is set as the Inactivity time, the network connection is maintained even though there is no data transmission. In this case, you should use the ‘Close’ command to close the connection.

This function is useful when there are two or more systems connected to the WIZ550S2E module. If one system is connected to the WIZ550S2E, other systems cannot connect to the module simultaneously. Therefore, the inactivity time should be set and the other system can connect to the module after the inactivity time is elapsed.

Inactivity Time can also be used if the TCP server system unexpectedly shuts down. In this case, there is no data communication, and WIZ550S2E will close the connection and enter into waiting state if the defined inactivity time elapses.


This is the interval time which WIZ550S2E tries to connect again after connection is closed. This is valid only in "TCP Client" or "TCP Mixed" having data from serial prior to TCP connection is established.

Serial Configurations


This menu is used for setting the serial port.

Baud Rate :
WIZ550S2E's Baud Rate
Data Bits :
WIZ550S2E's Data Bits (7,8,9)
Parity :
WIZ550S2E's Parity Bits
Stop Bits :
WIZ550S2E's stop Bits
Flow :
WIZ550S2E's Flow Control & RS422/RS485

AT Command

This function is controlling the module to allow the module could be capable to control the module through serial terminal (AT command).

Module Default setting: Enable
Default trigger to AT command: 2B 2B 2B in Hex.

Packing Conditions

Normally, data received from UART are sent to Ethernet immediately. But in many cases, users want to send data as a chunk of the whole frame without separated ones. This option is for packetizing data into one frame.

Time (0 ~ 65535 ms, ‘0’: Function Disable) : This field is for specifying time value (in ms) to judge whether one frame is received totally. If the time specified in this field is expired after receiving one byte, then WIZ550S2E notice one data frame is finished, make an Ethernet packet with all data in its serial buffer and send it to the peer system via Ethernet. If WIZ550S2E receives another byte from UART before the specified time is expired, it restart timer and add the received one to the end of serial data buffer. Size (0 ~ 255 byte, ‘0’: Function Disable) : This field is for specifying size value to judge whether one frame is received totally. If the size specified in this field is received, then WIZ550S2E notice one data frame is finished, make an Ethernet packet with specifying size's data in its serial buffer and send it to the peer system via Ethernet.
Char : This field is for specifying delimiter value to judge whether one frame is received totally. Char delimiters can be set up to 4 bytes in HEX and valid character count is decided according to the value in Length field. In case the value of Length field is '0', this option becomes inactivated. Appendix is another option for this. If user selects any value in Appendix field, WIZ550S2E make an ethernet packet with all received data by Char delimiter and next bytes in counts, which designated by Appendix field. When Appendix is set with any value, not '0', even though WIZ550S2E received Char delimiters, it will wait until it receives next data.

Options Configurations

Module Name

The device name is displayed in this area.
User can use this name to distinguish this module with others


This is password field for authentication.

Setting Password : Setting Password for Configuration Tool. Critical functions like "Setting", "Firmware Upload","Reset" and "Factory Reset" need this password to try issued action and avoid unauthorized users' command. When user wants to change its default Setting Password with new one, put new one in this field. Connection Password : When WIZ550S2E is TCP server, it needs connection password to check whether TCP client is an unauthorized user or not. After TCP Client is connected, it must transfer correct "Connection Password" within 3 seconds. Otherwise, WIZ550S2E will close its TCP connection.


This decides how to obtain IP address. If user selects "Use DHCP" then WIZ550S2E will obtain IP address dynamically by DHCP operation. Otherwise, it will operate in static mode.

Static mode :
If user uses this mode by deselecting "Use DHCP", user has to set WIZ550S2E with specific network information.

  1. First, select "MAC address" in "Search Windows"
  2. Then, IP setting section will be activated
  3. Fill those fields with information which user want to set.
  4. And press "Setting" button then network information will be changed with value user entered. DHCP mode : WIZ550S2E's network information will be set automatically without user's interference.


This is valid in TCP Client mode only. Normally, TCP Client mode has to know its peer system's IP address. But there are some cases where the IP address is unknown and especially when the IP address change frequently.
In this case, DNS function is needed.

User has to select “Use DNS” option and set DNS Server IP address and peer systems' Domain name in string. Put DNS Server IP, provided by ISP, into “DNS Server IP” field and peer system's Domain name into “Domain” field.