/* The port number is passed as an argument */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
void error(const char *msg)
{
perror(msg);
exit(1);
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno;
socklen_t clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
// create a socket
// socket(int domain, int type, int protocol)
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
// clear address structure
bzero((char *) &serv;_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
/* setup the host_addr structure for use in bind call */
// server byte order
serv_addr.sin_family = AF_INET;
// automatically be filled with current host's IP address
serv_addr.sin_addr.s_addr = INADDR_ANY;
// convert short integer value for port must be converted into network byte order
serv_addr.sin_port = htons(portno);
// bind(int fd, struct sockaddr *local_addr, socklen_t addr_length)
// bind() passes file descriptor, the address structure,
// and the length of the address structure
// This bind() call will bind the socket to the current IP address on port, portno
if (bind(sockfd, (struct sockaddr *) &serv;_addr,
sizeof(serv_addr)) < 0)
error("ERROR on binding");
// This listen() call tells the socket to listen to the incoming connections.
// The listen() function places all incoming connection into a backlog queue
// until accept() call accepts the connection.
// Here, we set the maximum size for the backlog queue to 5.
listen(sockfd,5);
// The accept() call actually accepts an incoming connection
clilen = sizeof(cli_addr);
// This accept() function will write the connecting client's address info
// into the the address structure and the size of that structure is clilen.
// The accept() returns a new socket file descriptor for the accepted connection.
// So, the original socket file descriptor can continue to be used
// for accepting new connections while the new socker file descriptor is used for
// communicating with the connected client.
newsockfd = accept(sockfd,
(struct sockaddr *) &cli;_addr, &clilen;);
if (newsockfd < 0)
error("ERROR on accept");
printf("server: got connection from %s port %d\n",
inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port));
// This send() function sends the 13 bytes of the string to the new socket
send(newsockfd, "Hello, world!\n", 13, 0);
bzero(buffer,256);
n = read(newsockfd,buffer,255);
if (n < 0) error("ERROR reading from socket");
printf("Here is the message: %s\n",buffer);
close(newsockfd);
close(sockfd);
return 0;
} Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!
OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.
#include <iostream>
#include <string>
using namespace std;
int main()
{
string name;
cout << "Enter name:";
getline (cin, name);
cout << "Hello " << name;
return 0;
}
C++ is a widely used middle-level programming language.
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
//code
}
else {
//code
}
You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.
Switch is an alternative to If-Else-If ladder.
switch(conditional-expression){
case value1:
// code
break; // optional
case value2:
// code
break; // optional
......
default:
code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while (condition) {
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (condition);
Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.
return_type function_name(parameters);
function_name (parameters)
return_type function_name(parameters) {
// code
}