When you connect to an SMPP server, there are three different types of connections that can be supported.
• A "sender" or "send only" connection is allowed to transmit messages only through the connection, it can not receive messages. (Some SMPP servers will continue to deliver SMPP delivery receipt messages over a "sender" connection.)
• A "receiver" or "receive only" connection is not allowed to transmit messages through the connection, it can only receive messages. Any attempt to receive messages through this connection will normally result in the error ESME_RINVBNDSTS (Incorrect BIND Status for the given command). If you see the ESME_RINVBNDSTS error when sending messages, verify that NowSMS has not been configured inadvertently for a receiver-only connection.
• A "transceiver" connection is allowed to send and transmit messages through the same connection.
When defining an SMPP connection in NowSMS, it is possible to configure the connection to be only a "sender", only a "receiver", separate "sender" and "receiver" connections, or a single "transceiver" connection.
The type of connection you use will depend on the preferences and policies of your SMPP service provider. Generally, separate "sender" and "receiver" connections offer the best performance under extreme loads, however your provider may want you to use a "transceiver" connection to reduce the connection overhead on your server.
There are also special settings where you may need to set up a connection to be just a "sender", or just a "receiver".
To define only a "sender" connection, make sure that the following options are applied in the properties of the SMPP connection:
• Do not check "Receive SMS messages".
• In "Advanced Settings", you should not check "Send and receive messages over the same connection".