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Asked: 2026-05-23T00:34:28+00:00

I modified beej’s guide to networking example (as seen below) to pass back a

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I modified beej’s guide to networking example (as seen below) to pass back a html response to a browser. I am getting “The connection was reset” every few refreshes, and can’t seem to figure out why? Its as if it is closing the connection before it sends out the html response.

Any ideas, or suggestions to debug?

Edit: It does sometimes pass the correct data to the browser.

Here is the code:

/*
 ** server.c -- a stream socket server demo
 */

#include <iostream>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>

#define PORT "8080"  // the port users will be connecting to

#define BACKLOG 10000    // how many pending connections queue will hold

using namespace std;

void sigchld_handler(int s)
{
    while(waitpid(-1, NULL, WNOHANG) > 0);
}

// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
    int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_storage their_addr; // connector's address information
    socklen_t sin_size;
    struct sigaction sa;
    int yes=1;
    char s[INET6_ADDRSTRLEN];
    int rv;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE; // use my IP

    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and bind to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                        p->ai_protocol)) == -1) {
            perror("server: socket");
            continue;
        }

        if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
                    sizeof(int)) == -1) {
            perror("setsockopt");
            exit(1);
        }

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("server: bind");
            continue;
        }

        break;
    }

    if (p == NULL)  {
        fprintf(stderr, "server: failed to bind\n");
        return 2;
    }

    freeaddrinfo(servinfo); // all done with this structure

    if (listen(sockfd, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }

    sa.sa_handler = sigchld_handler; // reap all dead processes
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
        perror("sigaction");
        exit(1);
    }

    printf("server: waiting for connections...\n");

    while(1) {  // main accept() loop
        sin_size = sizeof their_addr;
        new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
        if (new_fd == -1) {
            cout << "accept fail" << endl;
            continue;
        }

        inet_ntop(their_addr.ss_family,
                get_in_addr((struct sockaddr *)&their_addr),
                s, sizeof s);
        printf("server: got connection from %s\n", s);

        if (!fork()) { // this is the child process
            close(sockfd); // child doesn't need the listener
            string response = "HTTP/1.0 200 OK\r\n\r\n<html><head><title>Test</title></head><body>ok!</body></html>";
            if (send(new_fd, response.c_str(), response.length(), 0) == -1)
                cout << "error" << endl;
            close(new_fd);
            cout << "sent." << endl;
            exit(0);
        }
        close(new_fd);  // parent doesn't need this
    }

    return 0;
}
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1 Answer

  1. Editorial Team

    So there’s 2 errors here (3 really, the last one being that if you want to talk to a browser you really have to implement HTTP properly which is non-trivial)

    1. You’re sending the response immediately when you accept a client. A browser being a bit slow might then receive a response even before it’s finished sending a request – which’ll confuse the browser.

    2. You’re not reading the request. That means when you close the socket, there’ll be unread data, this’ll lead to a TCP RST (which causes “connection reset …. ” errors) being sent when you close the socket. In some cases the browser would have read the response before that happens, in other cases it might not, (and in some cases, I’d guess it’ll be confused as you have no Content-Length: header, so the browser doesn’t know if it ws supposed to receive more data when it encounters a TCP RST). This particular case is described better here

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