How to send SMS through SMPP from OpenAI Codex
This guide explains how to connect OpenAI Codex to Ozeki SMS Gateway's built in SMS MCP server, enabling the AI assistant to send and receive SMS messages through your own on-premises SMS gateway. You will learn how to install Ozeki SMS Gateway, create an MCP user account, generate an API key, register the MCP endpoint in Codex, and verify the setup by sending a test message.
Solution: How to send SMS from Codex
Codex connects to the SMPP SMS MCP Server through the MCP protocol, where Codex acts as the MCP client and Ozeki SMS Gateway acts as the MCP server. Ozeki SMS Gateway is installed on your local machine or server and connects to the SMS service provider over the internet using an SMPP client connection. When an SMS is sent, it first travels from Codex to the Ozeki SMS Gateway as an MCP tool call, and the gateway forwards it to the SMS service provider over SMPP, which delivers it to the recipient's mobile phone.
What is OpenAI Codex?
OpenAI Codex is a terminal-based AI coding agent developed by OpenAI that allows developers to interact with AI models directly from the command line. It can read and write files, execute commands, and call external tools through MCP servers, making it a powerful assistant for automating development workflows.
What is an SMPP SMS MCP Server?
An SMPP SMS MCP Server is a standardized software bridge that uses the Model Context Protocol to connect AI assistants (like Claude) to an SMS gateway system such as Ozeki SMS Gateway, which in turn delivers messages to the mobile network over an SMPP client connection. It exposes tools like "send_message" or "list_incomings" that an AI can autonomously call to perform real-world texting tasks without custom coding. This allows users to simply ask an AI to "send John a reminder text" and have the AI securely execute the action through the server. The SMS MCP Server built into Ozeki SMS Gateway also makes receiving SMS messages possible.
Download Ozeki SMS Gateway
To use this solution you need to install the SMS Gateway on your system.
Download the software: SMS Gateway
https://ozeki-sms-gateway.com/p_727-download-sms-gateway.html
Steps to follow
You will need Codex installed on your system, you can download it from here: https://openai.com/codex/.
- Install Ozeki SMS Gateway
- Setup the SMPP SMS connection
- Create an MCP user account
- Codex SMS MCP Server Config
- Add the SMS MCP Server config to Codex
- Send a test SMS
- Check the SMS in the SMS Gateway logs
Install Ozeki SMS Gateway
For a full tutorial on installing Ozeki SMS Gateway, check out our How to install Ozeki SMS Gateway on Windows guide.
Before you can use the SMS MCP Server, you need to install Ozeki SMS Gateway on your Windows machine or server. Download the installer zip file from the website, extract it, and run the executable to complete the installation. Once installed, the gateway will start automatically and its web-based management interface will be accessible from your browser.
Setup the SMPP SMS connection
For a full tutorial on setting up an SMPP Client connection, check out our SMPP Client Connection guide.
Before creating the MCP user, you need to connect Ozeki SMS Gateway to the mobile network by setting up an SMPP client. In the Connections panel, select Add new connection, and install a new SMPP client connection. Enter the host, port, and credentials provided by your SMS service provider, then save and activate the connection to bring the gateway online.
Create an MCP user account
For a full tutorial on creating an MCP User, check out our Create an MCP User guide.
Click Add new user/application, and select the MCP user type from the list. Enter a username and password for the account, then open the Advanced tab to generate an API key. Copy this key and store it in a safe location, as you will need it in the next steps.
Codex MCP server configuration
# Codex configuration file location:
C:\Users\%USERPROFILE%\.codex\config.toml
# Add the following block under the mcpServers section in config.yaml
# Replace {address} with your Ozeki SMS Gateway host IP
# Replace your-bearer-token with your API key
[mcp_servers.Ozeki]
url = "http://{address}:9529/mcp"
http_headers = { "Authorization" = "Bearer your-bearer-token" }
Example prompt
Send an SMS to +36301234567, the message should be "Hello from Codex".
Add the SMS MCP Server config to Codex
The following video shows how to add the Ozeki SMPP SMS MCP Server to Codex step-by-step.
Navigate to the Codex configuration directory at
C:\Users\%USERPROFILE%\.codex\ using File Explorer. You can open
this folder quickly by typing %USERPROFILE%\.codex directly into
the File Explorer address bar and pressing Enter (Figure 1).
Open the config.toml file in a text editor such as Notepad. This file
stores all Codex configuration, including any MCP servers that Codex should
connect to on startup (Figure 2).
Add the Ozeki SMPP SMS MCP Server entry to the file as shown below. Replace
{address} with the IP address or hostname of your Ozeki SMS Gateway
installation, and replace the Bearer token with the API key you generated for
your MCP user account (Figure 3).
[mcp_servers.Ozeki]
url = "http://{address}:9529/mcp"
http_headers = { "Authorization" = "Bearer your-bearer-token" }
Save the configuration file and close the text editor. The changes will take effect the next time Codex is started (Figure 4).
Open a terminal window by searching for Terminal in the Start menu. It is important to open a fresh terminal session after editing the configuration file so that Codex loads the updated settings (Figure 5).
Type codex and press Enter to launch Codex. It will start up and
attempt to connect to all MCP servers listed in the configuration file (Figure 6).
codex
Once Codex has started, run the /mcp command to display the
connection status of all configured MCP servers. Verify that the Ozeki
server is listed and its status shows as connected, confirming that Codex has
successfully reached your SMS gateway (Figure 7).
/mcp
Send a test SMS
The following video shows how to send an SMS message from Codex using the Ozeki SMPP SMS MCP Server step-by-step.
In the Codex prompt, type your SMS request in plain language and press Enter. The AI agent will interpret the request and invoke the appropriate MCP tool to deliver the message (Figure 8).
Send an SMS to +36301234567, the message should be "Hello from Codex".
Codex may ask for your approval before invoking the SMS tool. Review the proposed tool call and confirm to allow the AI agent to proceed (Figure 9).
Once the tool has been executed, the result will appear in the Codex terminal. A successful response confirms that the message was submitted to the gateway and handed off for delivery (Figure 10).
Check the SMS in the SMS Gateway logs
The following video shows how to check the SMS in the logs in Ozeki SMS Gateway step-by-step.
Open Ozeki SMS Gateway in your browser and navigate to the MCP user details page by clicking on the MCP user entry in the Users and applications panel (Figure 11).
In the MCP user event log, you should see an entry for the outgoing message, including the recipient number and message text, confirming that it was successfully processed by the gateway (Figure 12).
Final thoughts
In this guide, you have learned how to connect OpenAI Codex to Ozeki SMS Gateway's built-in SMS MCP Server and use it to send SMS messages directly from the terminal. By installing the gateway, setting up an SMPP connection to the mobile network, creating an MCP user account, and registering the MCP endpoint in Codex, you now have a fully functional on-premises SMS integration that your AI agent can use to communicate with any mobile phone.