Examples and practices described in this page don't take advantage of improvements introduced in later releases. Reading from and Writing to a Socket Let's look at a simple example that illustrates how a program can establish a connection to a server program using the Socket class and then, how the client can send data to and receive data from the server through the socket.
The listen Function The listen function converts an unconnected socket into a passive socket, indicating that the kernel should accept incoming connection requests directed to this socket.
It is defined as follows: The backlog argument provides an hint to the system of the number of outstanding connect requests that it should enqueue on behalf of the process. Once the queue is full, the system will reject additional connection requests.
The backlog value must be chosen based on the expected load of the server. The function listen return 0 if it succeeds, -1 on error. The accept Function The accept is used to retrieve a connect request and convert that into a request. The cliaddr and addrlen arguments are used to return the protocol address of the client.
The new socket descriptor has the same socket type and address family of the original socket. The original socket passed to accept is not associated with the connection, but instead remains available to receive additional connect requests.
The kernel creates one connected socket for each client connection that is accepted. Otherwise, before calling the accept function, the cliaddr parameter has to be set to a buffer large enough to hold the address and set the interger pointed by addrlen to the size of the buffer.
The send Function Since a socket endpoint is represented as a file descriptor, we can use read and write to communicate with a socket as long as it is connected. However, if we want to specify options we need another set of functions.
For example, send is similar to write but allows to specify some options.
The additional argument flags is used to specify how we want the data to be transmitted. We will not consider the possible options in this course.
We will assume it equal to 0. The function returns the number of bytes if it succeeds, -1 on error. The receive Function The recv function is similar to readbut allows to specify some options to control how the data are received.
It returns 0 if it succeeds, -1 on error. UDP is a connection-less, unreliable, datagram protocol TCP is instead connection-oriented, reliable and stream based.
Figure 4 shows the the interaction between a UDP client and server. First of all, the client does not establish a connection with the server. Instead, the client just sends a datagram to the server using the sendto function which requires the address of the destination as a parameter.
Similarly, the server does not accept a connection from a client.
Instead, the server just calls the recvfrom function, which waits until data arrives from some client. As shown in the Figure, the steps of establishing a UDP socket communication on the client side are as follows: Create a socket using the socket function; Send and receive data by means of the recvfrom and sendto functions.A Simple Java UDP Server and UDP Client September 17, / 44 Comments / in Code Samples, Java, Software / by Dave For a class I am taking, we are testing out a simple UDP Server and UDP Client to demonstrate what each one does and how sockets work.
Before going into the details of this application "Echo Server UDP Example Java" it is advised to go through the network basics, sockets and binding and UDP basics.
After studying the first application on UDP protocol, let us go to the second application Echo Server. The Echo server sends back to the same client the message it received.
That is, when the server receives a message from the client, the server . Kurose/Ross only cover Java socket programming and not that is used to read or write the the implementation of a TCP based echo server to summarize the.
We will now use the elementary functions from the previous chapter to write a complete TCP client/server example. Our simple example is an echo server that performs the following steps: The client reads a line of text from its standard input and writes the line to the server. It reads input from the user on the standard input stream, and then forwards that text to the echo server by writing the text to the socket.
The server echoes the input back through the socket to the client. The client program reads and displays the data passed back to it from the server. Note that the EchoClient example both writes to and reads from its socket, thereby sending data to and receiving data from the .
The Echo Thread Pool Server Tutorial is intended to provide an introduction to the concept of thread pools. In Java, thread pools are most commonly utilized through the java.