Android Softphone with Call Forwarding
Budget: $30 – $250 USD
1. Platform
• Android 9
2. Core Functionality
• The app must accept incoming SIP calls from my Asterisk server.
• Upon receiving a SIP call:
1. The app does not answer the SIP call immediately.
2. It first initiates a GSM call to a number , this number can be obtained from incoming sip call information .
3. Only after the GSM call is answered, the app answers the SIP call.
4. At that moment, the audio streams are bridged:
• SIP RTP ↔ GSM audio path.
• If the GSM call is not answered or fails, the SIP call must be rejected or continue ringing (not
answered silently).
3. Audio Handling
• Full two-way audio bridging between SIP (RTP) and GSM telephony path.
• Must work when:
• Screen is off.
• Phone is locked.
• App is in background.
• Audio must not cut out, mute, or drop unexpectedly.
4. Background Operation
• SIP account must remain registered while the app is running.
• Must work when the display is off and the device is idle.
• Options:
• Use a foreground service with persistent notification to keep alive, OR
• Use push notifications (FCM) if implemented.
• Developer must ensure background restrictions are handled (whitelist instructions for users if
needed).
Compatibility
• Must run on Android 9 or any recent version .
• Must support:
• At least G.711 codec (default),G.729 preferred
• Must work with Asterisk PJSIP channel driver.
6. Configuration
• App should allow me to set:
• SIP server address, username, password.
• GSM destination number (where SIP calls should be redirected).
• Each installation of the app must allow login with a single SIP extension (server, username,
password) and must be able to redirect calls independently on multiple devices.
7. Testing & Delivery
• Developer must provide live AnyDesk access:
• I will send test SIP calls from my Asterisk server.
• I will verify GSM redirection works in real time.
• SIP call must not be answered until GSM is answered.
• Audio must flow both ways after connection.
• Test must be performed with screen off and device locked.
8. Final Delivery
• Full Android Studio project with source code.
• Build instructions
• Compiled APK for installation.
• Android 9
2. Core Functionality
• The app must accept incoming SIP calls from my Asterisk server.
• Upon receiving a SIP call:
1. The app does not answer the SIP call immediately.
2. It first initiates a GSM call to a number , this number can be obtained from incoming sip call information .
3. Only after the GSM call is answered, the app answers the SIP call.
4. At that moment, the audio streams are bridged:
• SIP RTP ↔ GSM audio path.
• If the GSM call is not answered or fails, the SIP call must be rejected or continue ringing (not
answered silently).
3. Audio Handling
• Full two-way audio bridging between SIP (RTP) and GSM telephony path.
• Must work when:
• Screen is off.
• Phone is locked.
• App is in background.
• Audio must not cut out, mute, or drop unexpectedly.
4. Background Operation
• SIP account must remain registered while the app is running.
• Must work when the display is off and the device is idle.
• Options:
• Use a foreground service with persistent notification to keep alive, OR
• Use push notifications (FCM) if implemented.
• Developer must ensure background restrictions are handled (whitelist instructions for users if
needed).
Compatibility
• Must run on Android 9 or any recent version .
• Must support:
• At least G.711 codec (default),G.729 preferred
• Must work with Asterisk PJSIP channel driver.
6. Configuration
• App should allow me to set:
• SIP server address, username, password.
• GSM destination number (where SIP calls should be redirected).
• Each installation of the app must allow login with a single SIP extension (server, username,
password) and must be able to redirect calls independently on multiple devices.
7. Testing & Delivery
• Developer must provide live AnyDesk access:
• I will send test SIP calls from my Asterisk server.
• I will verify GSM redirection works in real time.
• SIP call must not be answered until GSM is answered.
• Audio must flow both ways after connection.
• Test must be performed with screen off and device locked.
8. Final Delivery
• Full Android Studio project with source code.
• Build instructions
• Compiled APK for installation.