TCP Server-Client implementation in C - GeeksforGeeks

02 Feb, 2022
Prerequisites – Socket Programming in C/C++, TCP and UDP server using select, UDP Server-Client implementation in C If we are creating a connection between client and server using TCP then it has few functionality like, TCP is suited for applications that require high reliability, and transmission time is relatively less critical. It is used by other protocols like HTTP, HTTPs, FTP, SMTP, Telnet. TCP rearranges data packets in the order specified. There is absolute guarantee that the data transferred remains intact and arrives in the same order in which it was sent. TCP does Flow Control and requires three packets to set up a socket connection, before any user data can be sent. TCP handles reliability and congestion control. It also does error checking and error recovery. Erroneous packets are retransmitted from the source to the destination.
The entire process can be broken down into following steps: 
The entire process can be broken down into following steps:
TCP Server – 
using create(), Create TCP socket.using bind(), Bind the socket to server address.using listen(), put the server socket in a passive mode, where it waits for the client to approach the server to make a connectionusing accept(), At this point, connection is established between client and server, and they are ready to transfer data.Go back to Step 3.
using create(), Create TCP socket.
using bind(), Bind the socket to server address.
using listen(), put the server socket in a passive mode, where it waits for the client to approach the server to make a connection
using accept(), At this point, connection is established between client and server, and they are ready to transfer data.
Go back to Step 3.
TCP Client – 
Create TCP socket.connect newly created client socket to server.
Create TCP socket.
connect newly created client socket to server.
TCP Server:
C
#include <stdio.h>#include <netdb.h>#include <netinet/in.h>#include <stdlib.h>#include <string.h>#include <sys/socket.h>#include <sys/types.h>#define MAX 80#define PORT 8080#define SA struct sockaddr   // Function designed for chat between client and server.void func(int connfd){    char buff[MAX];    int n;    // infinite loop for chat    for (;;) {        bzero(buff, MAX);           // read the message from client and copy it in buffer        read(connfd, buff, sizeof(buff));        // print buffer which contains the client contents        printf("From client: %s\t To client : ", buff);        bzero(buff, MAX);        n = 0;        // copy server message in the buffer        while ((buff[n++] = getchar()) != '\n')            ;           // and send that buffer to client        write(connfd, buff, sizeof(buff));           // if msg contains "Exit" then server exit and chat ended.        if (strncmp("exit", buff, 4) == 0) {            printf("Server Exit...\n");            break;        }    }}   // Driver functionint main(){    int sockfd, connfd, len;    struct sockaddr_in servaddr, cli;       // socket create and verification    sockfd = socket(AF_INET, SOCK_STREAM, 0);    if (sockfd == -1) {        printf("socket creation failed...\n");        exit(0);    }    else        printf("Socket successfully created..\n");    bzero(&servaddr, sizeof(servaddr));       // assign IP, PORT    servaddr.sin_family = AF_INET;    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);    servaddr.sin_port = htons(PORT);       // Binding newly created socket to given IP and verification    if ((bind(sockfd, (SA*)&servaddr, sizeof(servaddr))) != 0) {        printf("socket bind failed...\n");        exit(0);    }    else        printf("Socket successfully binded..\n");       // Now server is ready to listen and verification    if ((listen(sockfd, 5)) != 0) {        printf("Listen failed...\n");        exit(0);    }    else        printf("Server listening..\n");    len = sizeof(cli);       // Accept the data packet from client and verification    connfd = accept(sockfd, (SA*)&cli, &len);    if (connfd < 0) {        printf("server accept failed...\n");        exit(0);    }    else        printf("server accept the client...\n");       // Function for chatting between client and server    func(connfd);       // After chatting close the socket    close(sockfd);}
TCP Client:
C
#include <netdb.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/socket.h>#define MAX 80#define PORT 8080#define SA struct sockaddrvoid func(int sockfd){    char buff[MAX];    int n;    for (;;) {        bzero(buff, sizeof(buff));        printf("Enter the string : ");        n = 0;        while ((buff[n++] = getchar()) != '\n')            ;        write(sockfd, buff, sizeof(buff));        bzero(buff, sizeof(buff));        read(sockfd, buff, sizeof(buff));        printf("From Server : %s", buff);        if ((strncmp(buff, "exit", 4)) == 0) {            printf("Client Exit...\n");            break;        }    }}   int main(){    int sockfd, connfd;    struct sockaddr_in servaddr, cli;       // socket create and verification    sockfd = socket(AF_INET, SOCK_STREAM, 0);    if (sockfd == -1) {        printf("socket creation failed...\n");        exit(0);    }    else        printf("Socket successfully created..\n");    bzero(&servaddr, sizeof(servaddr));       // assign IP, PORT    servaddr.sin_family = AF_INET;    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");    servaddr.sin_port = htons(PORT);       // connect the client socket to server socket    if (connect(sockfd, (SA*)&servaddr, sizeof(servaddr)) != 0) {        printf("connection with the server failed...\n");        exit(0);    }    else        printf("connected to the server..\n");       // function for chat    func(sockfd);       // close the socket    close(sockfd);}
Compilation – Server side: gcc server.c -o server ./server
Client side: gcc client.c -o client ./client
Output – 
Server side: 
Socket successfully created..
Socket successfully binded..
Server listening..
server accept the client...
From client: hi
     To client : hello
From client: exit
     To client : exit
Server Exit... 
Client side: 
Socket successfully created..
connected to the server..
Enter the string : hi
From Server : hello
Enter the string : exit
From Server : exit
Client Exit... 
Anviti_Sr
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c-network-programming
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C Language
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