shs.c - absolutely minimal web server in C (tested on 4.3 BSD for VAX with gcc 2.7.2.2) | See https://supratim-sanyal.blogspot.com/2019/04/deploying-single-greatest-piece-of.html

shs.c

/*
shs.c - simple http server for 4.3 BSD on VAX
Compiles with gcc version 2.7.2.2 vax-dec-bsd
Tweaked from David Egan's HTTP Server in C (https://dev-notes.eu/2018/06/http-server-in-c/)

For each connection accepted on the designated port, this
minimal server returns a single file (index.html).

# gcc -v
Reading specs from /usr/local/lib/gcc-lib/vax-dec-bsd/2.7.2.2/specs
gcc version 2.7.2.2
# gcc -o shs shs.c
# ./shs
report()
waiting on accept
waiting on accept
...

The binary can be downloaded from http://bit.ly/43bsdvax-httpd-wget
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <netdb.h> // for getnameinfo()

// Usual socket headers
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#include <arpa/inet.h>

#define SERVER_PORT 80

#define SIZE 1024
#define BACKLOG 10  // Passed to listen()
#define INET6_ADDRSTRLEN 46
#define NI_MAXSERV 32 

void report(struct sockaddr_in *serverAddress);

void setHttpHeader(char httpHeader[])
{
    // File object to return
    char line[100];
    char responseData[8000];
    FILE *htmlData = fopen("/var/www/index.html", "r");
    if(NULL==htmlData){printf("Cannot open index.html to send\n"); exit(1); }
    while (fgets(line, 100, htmlData) != 0) {
        strcat(responseData, line);
    }
    strcat(httpHeader, responseData);
}

int main(void)
{
    char httpHeader[8000] = "HTTP/1.1 200 OK\r\n\n";
    int listening=0;
    int clientSocket=0;

    // Socket setup: creates an endpoint for communication, returns a descriptor
    // -----------------------------------------------------------------------------------------------------------------
    int serverSocket = socket(
        AF_INET,      // Domain: specifies protocol family
        SOCK_STREAM,  // Type: specifies communication semantics
        0             // Protocol: 0 because there is a single protocol for the specified family
    );

    // Construct local address structure
    // -----------------------------------------------------------------------------------------------------------------
    struct sockaddr_in serverAddress;
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_port = htons(SERVER_PORT);
    serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);//inet_addr("127.0.0.1");

    // Bind socket to local address
    // -----------------------------------------------------------------------------------------------------------------
    // bind() assigns the address specified by serverAddress to the socket
    // referred to by the file descriptor serverSocket.
    bind(
        serverSocket,                         // file descriptor referring to a socket
        (struct sockaddr *) &serverAddress,   // Address to be assigned to the socket
        sizeof(serverAddress)                 // Size (bytes) of the address structure
    );

    // Mark socket to listen for incoming connections
    // -----------------------------------------------------------------------------------------------------------------
    listening = listen(serverSocket, BACKLOG);
    if (listening < 0) {
        printf("Error: The server is not listening.\n");
        return 1;
    }
    report(&serverAddress);     // Custom report function
    setHttpHeader(httpHeader);  // Custom function to set header

    // Wait for a connection, create a connected socket if a connection is pending
    // -----------------------------------------------------------------------------------------------------------------
    while(1) {
        printf("waiting on accept\n");   
        clientSocket = accept(serverSocket, NULL, NULL);
        send(clientSocket, httpHeader, sizeof(httpHeader), 0);
        close(clientSocket);
    }
    return 0;
}

void report(struct sockaddr_in *serverAddress)
{
    printf("report()\n");
}