I am using Angular 5 to send post request to send SMS through Bulksms : http://bulksms.com/
When making the request from Angular (client), I am facing this issue :
Origin http://TTTT:4200 is not allowed by Access-Control-Allow-Origin.
How can I correct this issue in BulkSMS ?
Regards,
Your browser's same-origin policy is restricting your Javascript code from accessing a third party (i.e. api.bulksms.com in this case) in the way in which you hoped to do it - and CORS (Cross-Origin Resource Sharing), which is a mechanism to relax those restrictions, is not relaxed enough to allow these requests (from you as an untrusted third party) either.
Wikipedia Same-origin policy : "Under the [same-origin] policy, a web browser permits scripts contained in a first web page to access data in a second web page, but only if both web pages have the same origin. An origin is defined as a combination of URI scheme, host name, and port number. This policy prevents a malicious script on one page from obtaining access to sensitive data on another web page". The Wikipedia page contains some good examples of the sorts of malicious Javascript code uses that the same-origin policy tries to limit.
It is important to note that these restrictions are only enforced by browsers: HTTP client code that is not running under a browser typically doesn't care about any of this.
For development purposes, there are some tools that can make your life easier - for example, you could use live-server to run a simple HTTP server which serves up your static files, while also using its --proxy option to route requests to api.bulksms.com and solve your same-origin policy problem in the process.
For production, a typical solution is to route your AJAX requests, which are destined for the third party service, via your own server (the one serving up your Javascript files to your browser), or a reverse proxy (which would front both your own and the third party service). If there is a server side to your application, you can make the HTTP requests to api.bulksms.com from there, using an HTTP client, and then have your Javascript code talk to your own server, to indirectly make the requests to bulksms.com. This also gives you the opportunity to add authentication headers on your server side, without your Javascript code ever having to know them (e.g. if you have one bulksms.com account, and many users able to use that account via your Angular app, but who should not know your credentials). Similarly, you could impose limits on what your Angular users can do in this way (e.g. to limit the number of SMSs they could each send per day).