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@suyash
Created January 2, 2017 16:36
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TCP echo client-server in C
#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
int main() {
const char* server_name = "localhost";
const int server_port = 8877;
struct sockaddr_in server_address;
memset(&server_address, 0, sizeof(server_address));
server_address.sin_family = AF_INET;
// creates binary representation of server name
// and stores it as sin_addr
// http://beej.us/guide/bgnet/output/html/multipage/inet_ntopman.html
inet_pton(AF_INET, server_name, &server_address.sin_addr);
// htons: port in network order format
server_address.sin_port = htons(server_port);
// open a stream socket
int sock;
if ((sock = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
printf("could not create socket\n");
return 1;
}
// TCP is connection oriented, a reliable connection
// **must** be established before any data is exchanged
if (connect(sock, (struct sockaddr*)&server_address,
sizeof(server_address)) < 0) {
printf("could not connect to server\n");
return 1;
}
// send
// data that will be sent to the server
const char* data_to_send = "Gangadhar Hi Shaktimaan hai";
send(sock, data_to_send, strlen(data_to_send), 0);
// receive
int n = 0;
int len = 0, maxlen = 100;
char buffer[maxlen];
char* pbuffer = buffer;
// will remain open until the server terminates the connection
while ((n = recv(sock, pbuffer, maxlen, 0)) > 0) {
pbuffer += n;
maxlen -= n;
len += n;
buffer[len] = '\0';
printf("received: '%s'\n", buffer);
}
// close the socket
close(sock);
return 0;
}
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
/**
* TCP Uses 2 types of sockets, the connection socket and the listen socket.
* The Goal is to separate the connection phase from the data exchange phase.
* */
int main(int argc, char *argv[]) {
// port to start the server on
int SERVER_PORT = 8877;
// socket address used for the server
struct sockaddr_in server_address;
memset(&server_address, 0, sizeof(server_address));
server_address.sin_family = AF_INET;
// htons: host to network short: transforms a value in host byte
// ordering format to a short value in network byte ordering format
server_address.sin_port = htons(SERVER_PORT);
// htonl: host to network long: same as htons but to long
server_address.sin_addr.s_addr = htonl(INADDR_ANY);
// create a TCP socket, creation returns -1 on failure
int listen_sock;
if ((listen_sock = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
printf("could not create listen socket\n");
return 1;
}
// bind it to listen to the incoming connections on the created server
// address, will return -1 on error
if ((bind(listen_sock, (struct sockaddr *)&server_address,
sizeof(server_address))) < 0) {
printf("could not bind socket\n");
return 1;
}
int wait_size = 16; // maximum number of waiting clients, after which
// dropping begins
if (listen(listen_sock, wait_size) < 0) {
printf("could not open socket for listening\n");
return 1;
}
// socket address used to store client address
struct sockaddr_in client_address;
int client_address_len = 0;
// run indefinitely
while (true) {
// open a new socket to transmit data per connection
int sock;
if ((sock =
accept(listen_sock, (struct sockaddr *)&client_address,
&client_address_len)) < 0) {
printf("could not open a socket to accept data\n");
return 1;
}
int n = 0;
int len = 0, maxlen = 100;
char buffer[maxlen];
char *pbuffer = buffer;
printf("client connected with ip address: %s\n",
inet_ntoa(client_address.sin_addr));
// keep running as long as the client keeps the connection open
while ((n = recv(sock, pbuffer, maxlen, 0)) > 0) {
pbuffer += n;
maxlen -= n;
len += n;
printf("received: '%s'\n", buffer);
// echo received content back
send(sock, buffer, len, 0);
}
close(sock);
}
close(listen_sock);
return 0;
}
@yunzhi-wu
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In server.c, a string end char '\0' shall be put after the received string before printing (line 80).
pbuffer[0] = '\0';

@ayindriladutta
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bhalo hoyeche

@20zurmca
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20zurmca commented Aug 26, 2020

Hello. Could you explain what line 57 is doing in client.c Why add a terminator in the while loop? Is it because buffer gets overwritten after every recv call so we update the position of null terminator?

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