Java TCP Server and client sockets

Client-Server architecture in Java (TCP)

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite (IP), and is so common that the entire suite is often called TCP/IP. TCP provides reliable, ordered and error-checked delivery of a stream of octets between programs running on computers connected to a local area network, intranet or the public Internet. It resides at the transport layer. Web browsers use TCP when they connect to servers on the World Wide Web, and it is used to deliver email and transfer files from one location to another. HTTP, HTTPS, SMTP, POP3, IMAP, SSH, FTP, Telnet and a variety of other protocols are typically encapsulated in TCP.  This demonstrates how to setup a TCP Server and TCP Client in Java. A layer model is shown below


If you want to know more about the protocols read

If you just want to try sending code back and forth between two computers, grab the code below.




import*;class TCPServer
public static void main(String argv[]) throws Exception
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);

Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
System.out.println(“Received: ” + clientSentence);
capitalizedSentence = clientSentence.toUpperCase() + ‘\n’;

import*;class TCPClient
public static void main(String argv[]) throws Exception
String sentence;
String modifiedSentence;
BufferedReader inFromUser = new BufferedReader( new InputStreamReader(;
Socket clientSocket = new Socket(“localhost”, 6789);
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + ‘\n’);
modifiedSentence = inFromServer.readLine();
System.out.println(“FROM SERVER: ” + modifiedSentence);

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