Integrating an SMS gateway into your C program allows you to send real-time notifications, OTPs, and alerts directly from your applications. In this guide, we’ll walk through how to add SMS Gateways for my C Program using Text.lk API.

🔧 Prerequisites #

Before you begin:

1. Text.lk account → Sign up and get your API Key from the dashboard.
2. C compiler (like gcc).
3. Installed libcurl (for the recommended method).

sudo apt-get install curl

sudo apt-get install curl

4. Installed curl (for the simplest method).

sudo apt-get install libcurl4-openssl-dev

sudo apt-get install libcurl4-openssl-dev

🚀 Method 1: Recommended Way (Using libcurl) #

If you need more control (like checking if SMS was delivered), use libcurl inside your C program.

✅ Example Code (Method 1) #

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

int main(void) {
    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();
    if(curl) {
        const char *url = "https://app.text.lk/api/v3/sms/send";
        const char *data = "{"
            "\"recipient\":\"94710000000\","
            "\"sender_id\":\"TextLKDemo\","
            "\"type\":\"plain\","
            "\"message\":\"This is a test message\""
        "}";

        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Authorization: Bearer API_KEY");
        headers = curl_slist_append(headers, "Content-Type: application/json");
        headers = curl_slist_append(headers, "Accept: application/json");

        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);

        res = curl_easy_perform(curl);

        if(res != CURLE_OK) {
            fprintf(stderr, "Request failed: %s\n", curl_easy_strerror(res));
        } else {
            printf("SMS request sent successfully!\n");
        }

        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
    }
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

int main(void) {
    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();
    if(curl) {
        const char *url = "https://app.text.lk/api/v3/sms/send";
        const char *data = "{"
            "\"recipient\":\"94710000000\","
            "\"sender_id\":\"TextLKDemo\","
            "\"type\":\"plain\","
            "\"message\":\"This is a test message\""
        "}";

        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Authorization: Bearer API_KEY");
        headers = curl_slist_append(headers, "Content-Type: application/json");
        headers = curl_slist_append(headers, "Accept: application/json");

        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);

        res = curl_easy_perform(curl);

        if(res != CURLE_OK) {
            fprintf(stderr, "Request failed: %s\n", curl_easy_strerror(res));
        } else {
            printf("SMS request sent successfully!\n");
        }

        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
    }
    return 0;
}

⚡ How to Compile & Run (Method 1) #

gcc send_sms.c -o send_sms -lcurl
./send_sms

gcc send_sms.c -o send_sms -lcurl
./send_sms

✅ You’ll see the SMS request sent successfully! If everything works.

⚖ Pros & Cons (Method 1) #

• ✅ More reliable and professional.
• ✅ Can handle response (e.g., success/failure, delivery ID).
• ❌ Slightly more code to write.
• ❌ Needs libcurl library installed.

🚀 Method 2: The Simplest Way (Using system() + curl) #

If you just want to send SMS with minimum code, you can run the curl command directly from your C program.

✅ Example Code (Method 2) #

#include <stdlib.h>

int main() {
    system("curl -X POST https://app.text.lk/api/v3/sms/send "
           "-H 'Authorization: Bearer API_KEY' "
           "-H 'Content-Type: application/json' "
           "-H 'Accept: application/json' "
           "-d '{\"recipient\":\"94710000000\",\"sender_id\":\"TextLKDemo\",\"type\":\"plain\",\"message\":\"This is a test message\"}'");

    return 0;
}

#include <stdlib.h>

int main() {
    system("curl -X POST https://app.text.lk/api/v3/sms/send "
           "-H 'Authorization: Bearer API_KEY' "
           "-H 'Content-Type: application/json' "
           "-H 'Accept: application/json' "
           "-d '{\"recipient\":\"94710000000\",\"sender_id\":\"TextLKDemo\",\"type\":\"plain\",\"message\":\"This is a test message\"}'");

    return 0;
}

⚡ How to Compile & Run (Method 2) #

1. Save file as send_sms.c
2. Compile:

gcc send_sms.c -o send_sms

gcc send_sms.c -o send_sms

3. Run:

./send_sms

./send_sms

✅ That’s it — your SMS will be sent!

⚖ Pros & Cons (Method 2) #

• ✅ Very easy (just a few lines of code).
• ✅ No extra libraries needed.
• ❌ You can’t easily check the response in C.
• ❌ Depends on curl being installed.

🔑 Replace with Your Own Details #

• API_KEY → Your Text.lk API Key
• 94710000000 → Recipient’s mobile number (with country code)
• TextLKDemo → Your approved sender ID
• “This is a test message” → Your SMS text

🎯 Conclusion #

• If you need response handling & reliability → Use Method 1 with libcurl.
• If you need quick & simple SMS sending → Use Method 2 with system() + curl.

With either method, you’ve now successfully integrated the Text.lk SMS Gateway into your C program! 🚀