| PostgreSQL 7.4.7 Documentation | ||||
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| Prev | Fast Backward | Chapter 44. Frontend/Backend Protocol | Fast Forward | Next |
This section describes the message flow and the semantics of each message type. (Details of the exact representation of each message appear in Section 44.4.) There are several different sub-protocols depending on the state of the connection: start-up, query, function call, COPY, and termination. There are also special provisions for asynchronous operations (including notification responses and command cancellation), which can occur at any time after the start-up phase.
To begin a session, a frontend opens a connection to the server and sends a startup message. This message includes the names of the user and of the database the user wants to connect to; it also identifies the particular protocol version to be used. (Optionally, the startup message can include additional settings for run-time parameters.) The server then uses this information and the contents of its configuration files (such as pg_hba.conf) to determine whether the connection is provisionally acceptable, and what additional authentication is required (if any).
The server then sends an appropriate authentication request message, to which the frontend must reply with an appropriate authentication response message (such as a password). In principle the authentication request/response cycle could require multiple iterations, but none of the present authentication methods use more than one request and response. In some methods, no response at all is needed from the frontend, and so no authentication request occurs.
The authentication cycle ends with the server either rejecting the connection attempt (ErrorResponse), or sending AuthenticationOk.
The possible messages from the server in this phase are:
The connection attempt has been rejected. The server then immediately closes the connection.
The authentication exchange is successfully completed.
The frontend must now take part in a Kerberos V4 authentication dialog (not described here, part of the Kerberos specification) with the server. If this is successful, the server responds with an AuthenticationOk, otherwise it responds with an ErrorResponse.
The frontend must now take part in a Kerberos V5 authentication dialog (not described here, part of the Kerberos specification) with the server. If this is successful, the server responds with an AuthenticationOk, otherwise it responds with an ErrorResponse.
The frontend must now send a PasswordMessage containing the password in clear-text form. If this is the correct password, the server responds with an AuthenticationOk, otherwise it responds with an ErrorResponse.
The frontend must now send a PasswordMessage containing the password encrypted via crypt(3), using the 2-character salt specified in the AuthenticationCryptPassword message. If this is the correct password, the server responds with an AuthenticationOk, otherwise it responds with an ErrorResponse.
The frontend must now send a PasswordMessage containing the password encrypted via MD5, using the 4-character salt specified in the AuthenticationMD5Password message. If this is the correct password, the server responds with an AuthenticationOk, otherwise it responds with an ErrorResponse.
This response is only possible for local Unix-domain connections on platforms that support SCM credential messages. The frontend must issue an SCM credential message and then send a single data byte. (The contents of the data byte are uninteresting; it's only used to ensure that the server waits long enough to receive the credential message.) If the credential is acceptable, the server responds with an AuthenticationOk, otherwise it responds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support the authentication method requested by the server, then it should immediately close the connection.
After having receivedonds with an ErrorResponse.
If the frontend does not support