25 April 2014

Create fake TCP server to test a port is up and running

Bambitroll @ 16:41
There might be a way easier way to do this but here is how I solved it.

What I needed was to have a mock TCP server running on a given port on a given server to check that the firewall between my machine and the remote machine was properly open for a given port.
So I got a little  program running on the remote machine listening on the given port.
I also found a little client program, but using telnet works as well.

Under linux, just run "gcc server.c -o server_test" to compile the program and then run it with "server_test "
Also run "gcc client.c -o client_test" to compile and then run the client with "client_test "

Here is server.c:
/* A simple server in the internet domain using TCP
   The port number is passed as an argument */
#include 
#include 
#include 
#include 
#include  
#include 
#include 

void error(const char *msg)
{
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[])
{
     int sockfd, newsockfd, portno;
     socklen_t clilen;
     char buffer[256];
     struct sockaddr_in serv_addr, cli_addr;
     int n;
     if (argc < 2) {
         fprintf(stderr,"ERROR, no port provided\n");
         exit(1);
     }
     sockfd = socket(AF_INET, SOCK_STREAM, 0);
     if (sockfd < 0) 
        error("ERROR opening socket");
     bzero((char *) &serv_addr, sizeof(serv_addr));
     portno = atoi(argv[1]);
     serv_addr.sin_family = AF_INET;
     serv_addr.sin_addr.s_addr = INADDR_ANY;
     serv_addr.sin_port = htons(portno);
     if (bind(sockfd, (struct sockaddr *) &serv_addr,
              sizeof(serv_addr)) < 0) 
              error("ERROR on binding");
     listen(sockfd,5);
     clilen = sizeof(cli_addr);
     newsockfd = accept(sockfd, 
                 (struct sockaddr *) &cli_addr, 
                 &clilen);
     if (newsockfd < 0) 
          error("ERROR on accept");
     bzero(buffer,256);
     n = read(newsockfd,buffer,255);
     if (n < 0) error("ERROR reading from socket");
     printf("Here is the message: %s\n",buffer);
     n = write(newsockfd,"I got your message",18);
     if (n < 0) error("ERROR writing to socket");
     close(newsockfd);
     close(sockfd);
     return 0; 
}

Here is client.c:
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include  

void error(const char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sockfd, portno, n;
    struct sockaddr_in serv_addr;
    struct hostent *server;

    char buffer[256];
    if (argc < 3) {
       fprintf(stderr,"usage %s hostname port\n", argv[0]);
       exit(0);
    }
    portno = atoi(argv[2]);
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) 
        error("ERROR opening socket");
    server = gethostbyname(argv[1]);
    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) 
        error("ERROR connecting");
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);
    n = write(sockfd,buffer,strlen(buffer));
    if (n < 0) 
         error("ERROR writing to socket");
    bzero(buffer,256);
    n = read(sockfd,buffer,255);
    if (n < 0) 
         error("ERROR reading from socket");
    printf("%s\n",buffer);
    close(sockfd);
    return 0;
}



Sources: Linux Howtos: C/C++ -> Sockets Tutorial

09 April 2014

Adding/Removing queue to/from ActiveMQ via command line

Bambitroll @ 10:09

There is a way to add/remove queues on ActiveMQ from the command line.
It uses the REST interface of Jolokia which comes with Hawtio on ActiveMQ 5.9.0.

The first 2 commands contain all you need to create and then to remove the queue called q_titi, using the user admin/admin:
curl -u admin:admin -d "{\"type\":\"exec\",\"mbean\":\"org.apache.activemq:type=Broker,brokerName=localhost\",\"operation\":\"addQueue(java.lang.String)\",\"arguments\":[\"q_titi\"]}" http://localhost:8161/hawtio/jolokia/

curl -u admin:admin -d "{\"type\":\"exec\",\"mbean\":\"org.apache.activemq:type=Broker,brokerName=localhost\",\"operation\":\"removeQueue(java.lang.String)\",\"arguments\":[\"q_titi\"]}" http://localhost:8161/hawtio/jolokia/


The next 2 command do the same for the queue q_OMG but use the attached files for the necessary JSON request (so no more need to escape the double quotes and way more readable!):

curl -u admin:admin -d "@/tmp/jmr/createQ_json.txt" http://localhost:8161/hawtio/jolokia/
curl -u admin:admin -d "@/tmp/jmr/removeQ_json.txt" http://localhost:8161/hawtio/jolokia/

createQ_json.txt looks like this:
{
 "type":"exec",
 "mbean":"org.apache.activemq:type=Broker,brokerName=localhost",
 "operation":"addQueue(java.lang.String)",
 "arguments":["q_OMG"]
}


removeQ_json.txt looks like this:
{
 "type":"exec",
 "mbean":"org.apache.activemq:type=Broker,brokerName=localhost",
 "operation":"removeQueue(java.lang.String)",
 "arguments":["q_OMG"]
}


More info here:
Monitoring ActiveMQ via HTTP http://www.jakubkorab.net/2013/11/monitoring-activemq-via-http.html