About Message client
PostgreSQL: Network Protocol Explained The PostgreSQL protocol is the communication protocol used by PostgreSQL, an open-source relational database management system (RDBMS). The protocol establishes the rules and guidelines for how clients and servers interact when exchanging data and queries in a PostgreSQL environment.The PostgreSQL protocol is a client-server protocol, which means it involves two parties: the client application (e.g., a web application) and the server (the PostgreSQL database system). The protocol supports both simple and extended query cycles, as well as connection setup, query execution, and transaction management. It operates over a Transmission Control Protocol (TCP) connection or a Unix-domain socket.Here are the key components of the PostgreSQL protocol:Connection setup: Before communication can occur, the client must establish a connection with the PostgreSQL server. This involves exchanging startup messages, including the client’s PostgreSQL version, the desired database, and user authentication credentials. The server responds with an authentication request, and once the client successfully authenticates, the server sends a ‘Ready for Query’ message.Simple query cycle: This cycle involves the client sending a single SQL query to the server in a single message. The server processes the query, returns the result (if any), and sends a ‘Ready for Query’ message to indicate that it’s ready for the next query.Extended query cycle: This cycle supports more complex queries, such as those involving prepared statements and parameterized queries. The extended query cycle consists of several steps, including: a. Parse: The client sends a ‘Parse’ message with the SQL query and parameter types. The server acknowledges the message with a ‘Parse Complete’ message. b. Bind: The client sends a ‘Bind’ message to associate the prepared statement with a specific set of parameter values. The server acknowledges with a ‘Bind Complete’ message. c. Describe (optional): The client can send a ‘Describe’ message to request information about the prepared statement or the portal. The server responds with a ‘Row Description’ message or a ‘No Data’ message. d. Execute: The client sends an ‘Execute’ message to execute the prepared statement. The server sends the query result (if any) and a ‘Command Complete’ message. e. Sync: The client sends a ‘Sync’ message, and the server responds with a ‘Ready for Query’ message.SSL/TLS encryption: The PostgreSQL protocol supports optional encryption using SSL/TLS to secure data in transit between the client and server.Error handling and notifications: The protocol defines various error and notice response messages that the server can send to inform the client about issues or events related to the connection, query execution, or other aspects of database operation.Connection termination: To close the connection, the client sends a ‘Terminate’ message, and the server closes the socket.The PostgreSQL protocol is designed for efficiency and extensibility. It allows for the exchange of
Key features of the Message client that are enabled through these drivers include:
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A DHCP client device acquires the IP address and the network parameters by broadcasting a UDP packet called DHCPDISCOVER within the network.Upon receiving the DHCPDISCOVER broadcast, all the non-authoritative servers discard or ignore the message. DHCP servers within the networks receive and process the broadcast packet.The DHCP Discover message contains details like: UDP Source Port 68 UDP Destination Port 67 Source IP 0.0.0.0 Destination IP 255.255.255.255 DHCPDISCOVER Packet contents Here, the source IP of the broadcast packet is 0.0.0, as the client device has not been assigned the IP address yet. With the destination IP as 255.255.255.255, the broadcast packet is sent to all the network devices, through a process called limited broadcast. Destination IP can be set to a particular subnet ID to enable a directed broadcast.Step 2: DHCP Server offers IP and network configuration parameters to client.When a valid DHCP server receives the DHCPDISCOVER broadcast message, it reserves an IP in its IP pool, and offers that IP on lease to the requesting client. It conveys its IP lease offer, the subnet mask, and default gateways to the requesting client through a DHCPOFFER message. UDP Source Port 68 UDP Destination Port 67 Source IP 192.168.31.9 Destination IP 255.255.255.255 DHCPDISCOVER Packet contents Here 192.168.31.9 is the DHCP server that offers an IP address from its pool. Traditionally, this offer message is sent to the client by specifying the clients hardware or MAC address.Step 3: Client acknowledges the required DHCP’s offer and requests the IP lease.Upon receiving a DHCPOFFER message, the client requests the assignment of the IP address offered through the DHCPOFFER message by sending a DHCPREQUEST message to the server. This message signals the DHCP server to allocate the offered IP address on lease to the client.On receiving more than one DHCPOFFER messages from the servers in the network, the client sends a DHCPREQ (DHCP Request) message only to the DHCP server whose message was received first by the client. Other offers are discarded or ignored. UDP Source Port 68 UDP Destination Port 67 Source IP 0.0.0.0 Destination IP 255.255.255.255 DHCPREQ Packet contents Step 4: DHCP Server acknowledges clients IP lease request.Upon receiving the DHCPREQUEST message, the DHCP server assigns the IP address to the client, and logs it in its data store. The server confirms the allocated IP address, subnet mask, and default gateway details by sending an DHCPACK (DHCP acknowledgement) message.The client can now start using the allocate IP and network parameters. UDP Source Port 68 UDP Destination Port 67 Source IP 192.168.31.9 Destination IP 255.255.255.255 DHCPACK Packet contents The DHCP client configures itself with the received network parameters.DHCP relay agentDevices can send broadcast messages only within the network they are a part of. They can
