C application server/client doesn't work in docker container

Question

I'm a newbie with Docker. I write a server/client (very simple) application which both of them run in the same container.

I'm working on OSX and it work perfectly when I connect the client to the server.

However, I can't connect my client to my server. Here's my code:

client.c:

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

int main(int argc, char *argv[])
{
    int sockfd = 0, n = 0;
    char recvBuff[1024];
    struct sockaddr_in serv_addr;

    if(argc != 2) {
      printf("\n Usage: %s <ip of server> \n",argv[0]);
      return 1;
    }
    memset(recvBuff, '0',sizeof(recvBuff));
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
      printf("\n Error : Could not create socket \n");
      return 1;
    }
    memset(&serv_addr, '0', sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(5000);
    if(inet_pton(AF_INET, argv[1], &serv_addr.sin_addr)<=0) {
      printf("\n inet_pton error occured\n");
      return 1;
    }

   int connect_value = connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
   if (connect_value < 0) {
     printf("Value of connect_value %d\n", connect_value);
     fprintf(stderr, "Value of errno: %d\n", errno);
     return (1);
   }

    while ( (n = read(sockfd, recvBuff, sizeof(recvBuff)-1)) > 0){
      recvBuff[n] = 0;
      if(fputs(recvBuff, stdout) == EOF)
        printf("\n Error : Fputs error\n");
    }
    if(n < 0)
      printf("\n Read error \n");
    return 0;
}

server.c

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>

int main(int argc, char *argv[])
{
    int listenfd = 0, connfd = 0;
    struct sockaddr_in serv_addr;

    char sendBuff[1025];
    time_t ticks;

    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    memset(&serv_addr, '0', sizeof(serv_addr));
    memset(sendBuff, '0', sizeof(sendBuff));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(5000);

    bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));

    listen(listenfd, 10);

    while(1)
    {
        connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);

        ticks = time(NULL);
        snprintf(sendBuff, sizeof(sendBuff), "%.24s\r\n", ctime(&ticks));
        write(connfd, sendBuff, strlen(sendBuff));

        close(connfd);
        sleep(1);
     }
}

the command line I use to launch my container:

docker run -it --security-opt seccomp=unconfined --mount type=bind,src=/Users/steven/Documents/eip/firmware_coit,dst=/bidon 987steven/eip_linux bash

I compile and run with the following way:

gcc server.c -o server && ./server

gcc client.c -o client && ./client 127.0.0.1

Error : Connect Failed Value of

connect_value -1

Value of errno: 111

I tried to figured out by myself before post on SO but most of the topic and read about:

how to connect unix-socket to docker-demon
docker.sock
docker container networking (offical documentation)

But didn't find anything that could solve my problem.

Just to be clear that I have a very few knowledge in network in general and newbie in docker. Please feel free to ask if you node additional information from me. Thanks

What's the return value of connect() call ? It is less than 0 but what it is ? Try to find that out, it will help you. — Mazhar, Oct 25 '17 at 07:52
What command did you run for connect and did you run both server and client in same containers? — Tarun Lalwani, Oct 25 '17 at 08:08
Hello @Mazhar and TarunLalwani. I edit my original post :) (And yes, I run the server and the client in same containers) — S7_0, Oct 26 '17 at 07:28
https://stackoverflow.com/questions/24319662/from-inside-of-a-docker-container-how-do-i-connect-to-the-localhost-of-the-mach — Fred, Oct 26 '17 at 08:33

score 1 · Answer 1 · answered Oct 27 '17 at 03:22

Problem solve !

I used to launch my container with the following way:

 docker run -it --security-opt seccomp=unconfined --mount type=bind,src=/Users/steven/Documents/eip/firmware_coit,dst=/bidon 987steven/eip_linux bash

But I only need to add to the command line:

--net="host"

Alternatively you can run a docker container with network settings set to host. Such a container will share the network stack with the docker host and from the container point of view, localhost (or 127.0.0.1) will refer to the docker host.

Source: From inside of a Docker container, how do I connect to the localhost of the machine?

C application server/client doesn't work in docker container

1 Answers1