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Port Status Checker Script in C Language

This is a simple script in the C Programming Language to test the port status of a remote address.

Requirements:

You will need the gcc package to compile the program:

For RHEL based distro’s:

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$ yum install gcc -y

For Debian based distro’s:

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$ apt install gcc -y

Check TCP Port Status in C Language:

Our file: test.c

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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>


int main(int argc, char *argv[]) {

    int portno     = 443;
    char *hostname = "google.com";

    int sockfd;
    struct sockaddr_in serv_addr;
    struct hostent *server;

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        error("Error opening socket\n");
    }

    server = gethostbyname(hostname);

    if (server == NULL) {
        fprintf(stderr,"ERROR, no such host\n");
        exit(0);
    }

    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr,
         (char *)&serv_addr.sin_addr.s_addr,
         server->h_length);

    serv_addr.sin_port = htons(portno);
    if (connect(sockfd,(struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
        printf("Port is Closed\n");
    } else {
        printf("Port is Open\n");
    }

    close(sockfd);
    return 0;
}

Compile:

Compile using gcc:

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$ gcc -o test test.c

Execute:

Execute the script:

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$ ./test
Port is Open

Thank You

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