Protocols #1, Echo Protocol

Today I set off on a mission to implement every major protocol of the Internet.  I will start with the echo protocol in C.



Code:

/* Copyright 2010 Joseph Lewis <joehms22@gmail.com>
 * GNU GPL v 3.0
 * 
 * TO COMPILE:
 * cc -lpthread echo.c
 * 
 */

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

void *print_message_function( void *ptr );
void *tcp_server( void *ptr );
void *udp_server( void *ptr );

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

/*Compares two strings for equality*/
int compare(char one[], char two[])
{
    int j = strncmp(one, two, 100);
    return (j == 0);
}

/*Show the help menu with the given program path.*/
void show_help(char name[])
{
    printf( "\n" );    
    printf( "Usage: %s [-t][-u] [-p portumber] \n", name);
    printf( "Starts a RFC 862 compliant echo server.\n");
    printf( "  -t  Start on TCP\n");
    printf( "  -u  Start on UDP\n");
    printf( "  -p  Start on port (number) Default: 7\n");
    printf( "  -?  Show this menu\n");
    printf( "Example:\n");
    printf( " %s -t -u -p 7\n", name);
    printf( "\n" );    
    exit(1);
}

//Globals
int tcp = 0;
int udp = 0;
int portnumber = 7;

int main ( int argc, char *argv[] )
{
    /*Parse command line arguments*/
    
    if ( argc != 1 ) /* If there are arguments parse them. */
    {
        int loc = 1; /* argv[0] should be program name */
        
        while( loc < argc )
        {
            //Display the help menu
            if( compare(argv[loc], "--help") || 
                compare(argv[loc], "-?") ||
                compare(argv[loc], "-h") )
            {
                show_help(argv[0]);
            }
            
            //The port number
            if( compare(argv[loc], "-p") )
            {
                if( loc + 1 >= argc ) //Too few arguments, display help
                {
                    argv[loc] = "--help";
                } else {
                    portnumber = atoi( argv[loc+1] );
                    loc += 1;
                }
            }
            
            if( compare(argv[loc], "-t") )
               tcp = 1;
            
            if( compare(argv[loc], "-u") )
               udp = 1;
            
            loc += 1;
        }
    }else{
        show_help(argv[0]);
    }
    
    
    pthread_t thread1, thread2;
    char *message1 = "Thread 1";

    /* Create independent threads each of which will execute function */

    pthread_create( &thread2, NULL, udp_server, (void*) message1);
    pthread_create( &thread1, NULL, tcp_server, (void*) message1);


    /* Wait untill threads are complete before main exits. */

    pthread_join( thread1, NULL);
    pthread_join( thread2, NULL); 

    exit(0);
}

void *print_message_function( void *ptr )
{
     char *message;
     message = (char *) ptr;
     printf("%s \n", message);
}

void *tcp_server( void *ptr )
{
     if(tcp)
     {
        printf("TCP started on port %i\n",portnumber);
        
        int sockfd, newsockfd, portno, clilen;
        char buffer[256];
        struct sockaddr_in serv_addr, cli_addr;
        int n;
        
        sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (sockfd < 0) error("ERROR opening socket");
        
        bzero((char *) &serv_addr, sizeof(serv_addr));
        
        portno = portnumber;
        serv_addr.sin_family = AF_INET;
        serv_addr.sin_addr.s_addr = INADDR_ANY;
        serv_addr.sin_port = htons(portnumber);
        if (bind(sockfd, (struct sockaddr *) &serv_addr,
              sizeof(serv_addr)) < 0) 
              error("ERROR on binding");
        while( 1 )
        {      
            listen(sockfd,5);
            clilen = sizeof(cli_addr);
            newsockfd = accept(sockfd, 
                     (struct sockaddr *) &cli_addr, 
                     &clilen);
            if (newsockfd < 0) 
              error("ERROR on accept");
            do
            {  
                bzero(buffer,256);
                n = read(newsockfd,buffer,255);
                if (n < 0) error("ERROR reading from socket");
                n = write(newsockfd,buffer,n);
                if (n < 0) error("ERROR writing to socket");
            }while( n > 0 );
        }
          
    }
}

void *udp_server( void *ptr )
{
     if(udp)
     {
         printf("UDP started on port %i\n",portnumber);
         
        int sock, length, fromlen, n;
        struct sockaddr_in server;
        struct sockaddr_in from;
        char buf[1024];

        sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock < 0) 
            error("Problem opening socket");
        
        length = sizeof(server);
        bzero(&server,length);
        
        server.sin_family = AF_INET;
        server.sin_addr.s_addr = INADDR_ANY;
        server.sin_port = htons(portnumber);
        
        if (bind(sock,(struct sockaddr *)&server,length)<0)
           error("Problem binding UDP");
        fromlen = sizeof(struct sockaddr_in);
        
        while( 1 ) 
        {
            n = recvfrom(sock,buf,1024,0,(struct sockaddr *)&from,&fromlen);
            if (n < 0) 
                error("recvfrom");
            n = sendto(sock,buf,n,0,(struct sockaddr *)&from,fromlen); //echo
            if (n < 0) 
                error("sendto");
        }
     }
}