Client Server Processes
In computer networks, the client-server model is a common architecture for distributing application logic between two types of processes: client processes and server processes.
A client process is typically an application program that initiates a request for a service from a server process, which is usually running on a remote computer system. The client process may be running on the same computer as the server process or on a different computer. When a client process sends a request to a server process, it waits for a response from the server before proceeding.
On the other hand, a server process is typically an application program that provides a service to client processes. The server process listens for incoming requests from client processes and responds to them accordingly. The server process may be running on a dedicated computer system, known as a server, or on the same computer as the client process.
In the client-server model, the communication between the client and server processes is typically done using a protocol, such as HTTP or TCP/IP. The client process sends a request to the server process using the protocol, and the server process responds with a reply, which may include the requested data or information about the status of the requested service.
Overall, the client-server model is a powerful architecture that enables distributed computing and allows application logic to be split between different processes, leading to more efficient and scalable systems.
The idea of a socket
A socket is a software endpoint that allows two processes to communicate over a computer network. A socket is identified by a unique combination of an IP address and a port number, and it provides a means for processes running on different computers to exchange data.
In computer networks, a socket is typically implemented using a programming interface known as a socket API, which allows applications to create, send, and receive data over a network. The socket API provides a set of functions that can be used to create and manage sockets, connect to remote servers, and send and receive data.
There are two main types of sockets: client sockets and server sockets. A client socket is typically created by an application that wants to connect to a server process running on a remote computer. The client socket is used to initiate the connection to the server and to send requests to the server for information or services.
On the other hand, a server socket is typically created by a server process that is listening for incoming connections from client processes. When a client attempts to connect to the server, the server socket accepts the connection request and creates a new socket for the communication to take place between the client and the server.
Overall, the use of sockets has become a fundamental concept in computer networks, as they provide a simple and efficient means for processes running on different computers to communicate with each other over a network. The socket API provides a powerful tool for software developers to create networked applications that can run on a wide range of platforms and devices.
Transport Services available to the Application Layer
In the Internet, there are two main transport layer protocols available for use by the application layer: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
TCP is a connection-oriented protocol that provides reliable, ordered delivery of data between applications. It ensures that data is transmitted without errors and that all data is received in the order it was sent. TCP is often used by applications that require reliable data transfer, such as email, file transfer, and web browsing.
UDP, on the other hand, is a connectionless protocol that does not guarantee the reliable delivery of data or the order in which it is received. It is often used by applications that require low latency and can tolerate some data loss, such as online gaming, video streaming, and voice-over IP (VoIP) applications.
Other transport layer protocols available on the Internet include SCTP (Stream Control Transmission Protocol) and DCCP (Datagram Congestion Control Protocol), but these are less commonly used than TCP and UDP.
TCP and UDP
TCP and UDP are two different transport layer protocols available on the Internet. While both of them provide a way for applications to send and receive data over the network, they differ in their characteristics, as well as in their advantages and disadvantages.
TCP ( Transmission Control Protocol)
TCP (Transmission Control Protocol) is a connection-oriented protocol that provides reliable, ordered delivery of data between applications. When a TCP connection is established between two hosts, they exchange messages to negotiate various parameters, such as the maximum segment size, window size, and sequence numbers. Once the connection is established, TCP guarantees that all data will be transmitted without errors and in the order it was sent. This is achieved through a process of flow control, congestion control, and error detection and correction.
The reliability of TCP comes at the cost of increased overhead and latency. Because TCP ensures that all data is transmitted reliably, it needs to establish a connection, maintain state information, and retransmit lost packets if necessary. This can result in higher latency and lower throughput than with UDP. However, for applications that require reliable data transfer, such as email, file transfer, and web browsing, TCP is the preferred choice.
UDP (User Datagram Protocol)
UDP (User Datagram Protocol) is a connectionless protocol that does not provide reliable, ordered delivery of data. Instead, UDP sends packets of data as individual datagrams, without establishing a connection first. UDP is a simple and lightweight protocol that is ideal for applications that require low latency and can tolerate some data loss, such as online gaming, video streaming, and voice-over IP (VoIP) applications.
Because UDP does not provide reliability, it is up to the application to handle any lost or out-of-order packets. This can be achieved through various techniques, such as error detection and correction, duplicate detection, and retransmission. However, these techniques add complexity to the application, and they may not always be necessary, depending on the specific requirements of the application.
Conclusion
In summary, TCP is a reliable, connection-oriented protocol that is suitable for applications that require ordered, error-free delivery of data. UDP is a lightweight, connectionless protocol that is suitable for applications that require low latency and can tolerate some data loss. The choice between TCP and UDP depends on the specific requirements of the application, and the trade-offs between reliability, latency, and overhead.
