# Inbound and two-way SMS: long codes, short codes, virtual numbers, keywords and autoresponders > Inbound and two-way SMS turn broadcast into a conversation: how receiving numbers work, short codes vs long/virtual numbers, keywords, autoresponders, webhooks and consent. - Canonical URL: https://www.broadnet.me/blog/inbound-and-two-way-sms - Language: en - Last updated: 2026-10-10 - Publisher: BroadNet (https://www.broadnet.me) - Published: 2018-01-25 - Author: BroadNet Editorial Team Most messaging programs start one-directional: you send, the customer reads. Inbound and two-way SMS turn that into a conversation. When a customer can text back — a keyword, a reply to a survey, a "STOP" — you gain a channel that confirms, captures and responds in the moment, on the phone number people already carry everywhere. Here is how inbound works, the number types behind it, and how to wire it into your systems without losing control of consent. ## How inbound SMS works Every inbound program starts with a number that can receive messages. When a customer sends a text to that number, the message travels from their handset to the mobile operator, across the operator network to BroadNet, and then to you. In telecom terms these are mobile-originated (MO) messages — originated by the mobile subscriber rather than by your application. What happens next is up to you. The platform can answer automatically, forward the message to your application, or both. Most teams connect inbound through a webhook: BroadNet posts each incoming message — the sender number, the number it was sent to, the text and a timestamp — to a URL you control, in real time. Your application reads it, decides what to do, and replies through the same API you use for outbound. ## The numbers: short codes, long codes and virtual numbers The receiving number shapes what your program can do, so choose it deliberately. - Short codes are five- or six-digit numbers built for high-volume, high-throughput messaging. They are easy to print and remember ("Text JOIN to 12345"), which makes them the natural home for keyword campaigns and any program that expects large bursts of inbound traffic. - Long codes and virtual numbers are standard-length mobile numbers. They carry lower throughput than a short code but reach across more markets and read as a normal phone number, which suits one-to-one conversations, support lines and regional programs. The practical trade-off is throughput and memorability versus reach and cost. A voting or campaign line that spikes to thousands of replies a minute wants a short code; a support or notification number that holds steady two-way threads is usually better served by a long or virtual number. BroadNet provisions inbound numbers across its operator footprint, so the choice can follow the use case and the country rather than a single default. ## Keywords and autoresponders A keyword is a word a customer texts to your number to trigger a defined action — JOIN, BALANCE, STOP, a competition code. On arrival, an autoresponder can send an immediate, pre-set reply: a confirmation, a link, a menu, or the next question in a flow. This runs without a person in the loop, which is what lets a single number handle opt-ins, quick lookups and campaign entries at scale. Autoresponders work best when they are specific. Reserve keywords that are short and unambiguous, reply instantly so the customer knows the message landed, and always define what happens when the text does not match a keyword — a fallback that points to help is better than silence. ## Two-way conversations and webhooks Autoresponders handle the predictable; two-way SMS handles everything else. Because each inbound message carries the customer's number, your application can tie it back to an account, an open ticket or an earlier message and continue the thread. A delivery confirmation reply becomes a status update; an answer to a survey question becomes the prompt for the next one; a customer question routes to an agent and back. The webhook is what makes this real. Rather than polling for new messages, your systems receive them as they arrive and respond programmatically. That immediacy is the difference between a broadcast tool and a conversation: the customer texts, your logic runs, and the reply is on its way in seconds. ## Where two-way SMS earns its place Inbound and two-way messaging tend to prove their value in a handful of recurring patterns: - Customer support — customers reply to a thread instead of calling, and agents pick up the conversation with full context. - Surveys and feedback — a question goes out, answers come back as inbound messages, and follow-ups branch on the reply. - Opt-in and opt-out — a keyword subscribes a customer; STOP unsubscribes them, cleanly and on the record. - Confirmations and alerts — appointment reminders and alerts that ask for a Y/N or a reschedule, handled in the same thread. - Lead capture — a printed or on-screen keyword turns an ad, poster or event into a list of consenting contacts. ## Consent stays with you Two-way SMS makes consent easier to manage, but it does not remove the obligation. Keep an explicit opt-in before you message someone, honour STOP and equivalent keywords immediately, and give people a plain way to reach a human. A clean, consent-based list protects deliverability and trust — the two things that keep an inbound program working over time. Inbound is not a bolt-on to outbound messaging; it is the other half of the same channel. Get the number type, the keywords and the webhook right, and SMS stops being something you send and becomes something you can have a conversation on.