C++ Retrieve data via SSH using libssh libary failed

Question

I'm trying to get the output of the command 'df' which I'll replace later, from a remote server:

#include <libssh/libssh.h>
#include <stdlib.h>
#include <stdio.h>

int main()
{
    ssh_session my_ssh_session;
    int rc;
    ssh_channel channel;
    char buffer[256];
    int nbytes;
    int port = 22;
    my_ssh_session = ssh_new();


    if (my_ssh_session == NULL)
    exit(-1);
    ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, "192.168.2.2");
    ssh_options_set(my_ssh_session, SSH_OPTIONS_PORT, &port);

    rc = ssh_connect(my_ssh_session);

    if (rc != SSH_OK)
            {
            fprintf(stderr, "Failed %s\n",
            ssh_get_error(my_ssh_session));
            exit(-1);
            }



    channel = ssh_channel_new(my_ssh_session);
    if (channel == NULL)
    return SSH_ERROR;

    rc = ssh_channel_open_session(channel);
    if (rc != SSH_OK)
            {
            ssh_channel_free(channel);
            return rc;
            }
    rc = ssh_channel_request_exec(channel, "df");
    if (rc != SSH_OK)
            {
            ssh_channel_close(channel);
            ssh_channel_free(channel);
            return rc;
            }
    nbytes = ssh_channel_read(channel, buffer, sizeof(buffer), 0);
    while (nbytes > 0)
            {
            if (write(1, buffer, nbytes) != nbytes)
                    {
                    ssh_channel_close(channel);
                    ssh_channel_free(channel);
                    return SSH_ERROR;
                    }
            nbytes = ssh_channel_read(channel, buffer, sizeof(buffer), 0);
            }
    if (nbytes < 0)
            {
            ssh_channel_close(channel);
            ssh_channel_free(channel);
            return SSH_ERROR;
            }
    ssh_channel_send_eof(channel);
    ssh_channel_close(channel);
    ssh_channel_free(channel);
    return SSH_OK;




ssh_disconnect(my_ssh_session);
ssh_free(my_ssh_session);
}

The compiler didn't show any errors, but there were no results when I run the program, I checked the syslog of the remote server and I found the following line:

sshd[12794]: dispatch_protocol_error: type 90 seq 3

Please advise what could be the problem,

Thank you.

Answer 1

It seems like you are trying to get to the remote server without functions of host authentification (e.g. checking information from /.ssh/known_hosts) and user authentificationa through public keys or password. You should place these two functions after the

if (rc != SSH_OK)
{
fprintf(stderr, "Failed %s\n", ssh_get_error(my_ssh_session));
exit(-1);
}

Look through the chapters 1 and 2 in libssh tutorial.