A DID number by itself is just an address in the carrier's network; the softphone connected to it over SIP is what rings and picks up. Between "number purchased" and "number ringing" sits one step — the connection setup — and that's where first-timers get stuck. Here's what parameters you need, how to tell the connection is up, why registration fails, and how to verify a number before relying on it.
What you need to connect
A softphone needs exactly five things, all issued with the number. The server address is the network point the softphone talks to — like a mail server address for an email client. The login is the account identifier, usually the number itself. The password proves the softphone may use that login. Current values are always in your dashboard next to the number.
The port tells the softphone which "door" of the server to knock on, and the transport defines the protocol: unencrypted, encrypted at the transport layer, or wrapped in a secured channel. Each transport has its own default port, and mixing parameters from two transports is a common reason a connection doesn't answer.
Registration — the first sign it's working
Once all five parameters are entered, the softphone sends a registration request and, if correct, gets confirmation back — usually a "registered" indicator or a green status. Until registration succeeds, the number exists on paper only: incoming calls have nowhere to go, and outgoing calls get rejected.
Registration isn't one-time; it's a process the softphone repeats at a set interval so the server knows the device is still there. If that interval is misconfigured or the network is unstable, status can "flicker" — and calls don't get through during those gaps.
Common reasons registration fails
Wrong transport is the most frequent mistake: if the server expects a secured connection and the softphone knocks unencrypted on another port, the request never finds its target. Port blocking comes next: a firewall may close non-standard ports, or a provider may throttle a traffic range by default.
Conflict with network equipment is less obvious but explains the most stubborn cases: some routers "help" voice traffic with built-in signaling handling and mangle packets until the server stops recognizing them. Turning that off often fixes it in a minute. Another cause is stale settings — the password changed in the account, but the softphone kept the old one.
Checking inbound and outbound calls separately
Successful registration only confirms the softphone and server see each other — it says nothing about whether a real call reaches you or your own call goes out. These two directions need separate checks: have someone call your DID number, and separately dial out yourself. Testing only one direction is why problems often surface during real work rather than setup.
If both directions connect but the other person hears you and you don't hear them, or vice versa, that's not a registration problem — it's the voice stream: signaling works, but audio gets blocked along the path.
What to do about one-way audio
One-way audio almost always means the voice stream is blocked in one direction by network equipment, even though registration and call-setup signaling went through fine. Check double NAT first: if two routers with address translation sit between the softphone and the internet, the stream often gets lost at the second one.
Next, temporarily disable built-in voice-traffic handling on the router and test again. If that doesn't help, try a different transport or network to isolate where audio is lost. Causes of poor sound at the codec level are covered separately in call quality on a DID number.
Connection security
Connection parameters are effectively the key to your number: whoever has them can place calls at your expense, so login, password, and server address should never be published — not in chats, not in screenshots. A second layer of defense is restricting connection sources: if your softphone always connects from one place, allow connections only from known addresses.
Don't leave an account registered on devices you no longer use, and rotate the password at the slightest suspicion it leaked. If a problem remains after that, describe it to support.
Frequently Asked Questions
Registration is up but calls don't go through — what's wrong?
Registration only confirms the softphone is talking to the server; it doesn't guarantee the call gets through. Check inbound and outbound calls separately, and confirm transport and port match what was issued for the number, not defaults from another profile.
Why does the registration status keep appearing and disappearing?
Usually an unstable network or too short a re-registration interval combined with channel delays. Check connection stability and, if possible, slightly increase the re-registration interval.
How do I know which transport to use for a specific number?
Transport and port are always listed with the other connection parameters when the number is issued. If parameters changed later, check current values where they originally came from, rather than guessing.
Connection parameters are issued with the number right after purchase; the whole process from choosing a country to a registered softphone takes minutes — the catalogue of DID numbers is in the DID numbers section on turbon.rent.