Simple TCP server with multiple clients C/unix

Here is your's modified server code to handle multiple clients using fork

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>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);    //Below code is modified to handle multiple clients using fork    //------------------------------------------------------------------    int pid;    while (1) {         newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);         if (newsockfd < 0)                error("ERROR on accept");         //fork new process         pid = fork();         if (pid < 0) {              error("ERROR in new process creation");         }         if (pid == 0) {            //child process            close(sockfd);            //do whatever you want            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);          } else {             //parent process             close(newsockfd);          }    }    //-------------------------------------------------------------------   return 0;}

Server.c

         #define RUNNING_DIR     "/tmp "        define LOCK_FILE       "exampled.lock"        #define LOG_FILE        "exampled.log"        #include <fcntl.h>   #include <signal.h>     #include <unistd.h>     #include <stdlib.h>     #include <sys/types.h>   #include  <sys/socket.h>   #include  <stdio.h>  #include  <netinet/in.h>     #include  <sys/time.h>      #include  <sys/ioctl.h>    #include  <unistd.h>    #include <string.h>  #include <arpa/inet.h>       #include <errno.h> #include <time.h>  #include <string.h>        #define MAXCLIENT 100        #define TRUE 1        #define FALSE 0       #define MINUTE 5      struct Client      {    char name[256];char *clientAddr;int fd;     };    int client;      int i;    int minute;    struct Client p[100];     void remove_client(int);      int search_addr(char [],int *);     void log_message(filename,message)char *filename;char *message;      {FILE *logfile;logfile=fopen(filename,"a");if(!logfile) return;fprintf(logfile,"%s\n",message);fclose(logfile);    }      void catch_int(sig)int sig;  {log_message(LOG_FILE,strsignal(sig));     }    void daemonize()   {int i,lfp,lfp1;char str[10];    signal(SIGINT, catch_int);for ( i=0;i<65;i++){    if ( i!=32 && i!=33 )        if (signal(i, SIG_IGN) != SIG_IGN)            signal(i, catch_int);}if(getppid()==1) return; /*    already a daemon */i=fork();if (i<0) exit(1); /*    fork error */if (i>0) exit(0); /*    parent exits *//*    child (daemon) continues */setsid(); /*    obtain a new process group */for (i=getdtablesize();i>=0;--i) close(i); /*    close all descriptors */i=open("/dev/null",O_RDWR); dup(i); dup(i); /*    handle standart I/O */umask(027); /*    set newly created file permissions */chdir(RUNNING_DIR); /*    change running directory */lfp=open(LOCK_FILE,O_RDWR|O_CREAT,0640);lfp1=open(LOG_FILE,O_RDWR|O_CREAT,0640);if (lfp<0) exit(1); /*    can not open */if (lockf(lfp,F_TLOCK,0)<0) exit(0); /*    can not lock *//*    first instance continues */sprintf(str,"%d\n",getpid());write(lfp,str,strlen(str)); /*    record pid to lockfile */   }       int main()         {     daemonize();   time_t rawtime;  struct tm *info;      time(&rawtime);     info = localtime(&rawtime );     minute=MINUTE + info->tm_min;      int server_sockfd, client_sockfd;     int server_len, client_len;      struct sockaddr_in server_address;       struct sockaddr_in client_address;      int result;        fd_set readfds, testfds;server_sockfd = socket(AF_INET, SOCK_STREAM, 0);server_address.sin_family = AF_INET;server_address.sin_addr.s_addr = htonl(INADDR_ANY);server_address.sin_port = htons(5000);server_len = sizeof(server_address);bind(server_sockfd, (struct sockaddr *)&server_address, server_len);listen(server_sockfd, 5);FD_ZERO(&readfds);FD_SET(server_sockfd, &readfds);while(1) {    char ch;    int fd;    int nread;    testfds = readfds;    result = select(FD_SETSIZE,&testfds,NULL,NULL,NULL);    if(result < 1) {        perror("server5");        exit(1);    }    for(fd = 0; fd < FD_SETSIZE; fd++) {        time(&rawtime);        info = localtime(&rawtime );        if(FD_ISSET(fd,&testfds)) {            if(fd == server_sockfd) {                int j=0;                char Clients[1096];                memset( Clients, '\0', sizeof(Clients) );                client_len = sizeof(client_address);                client_sockfd = accept(server_sockfd,                        (struct sockaddr          *)&client_address, &client_len);                client++;                char *sAddress = inet_ntoa(client_address.sin_addr);                p[i].clientAddr=strdup(sAddress);                sprintf(p[i].name,"client%d",client);                p[i].fd=client_sockfd;                for (j =0; j < client; j++)                {                    strcat(Clients,p[j].clientAddr);                    strcat(Clients," ");                    strcat(Clients,p[j].name);                     strcat(Clients,"\n");                  }                for ( j=0; j < client ; j++)                {                    send(p[j].fd,Clients,strlen(Clients),0);                }                i++;                FD_SET(client_sockfd, &readfds);            }            else {                ioctl(fd, FIONREAD, &nread);                if(nread == 0) {                    close(fd);                    remove_client(fd);                    FD_CLR(fd, &readfds);                }                else {                    char addr[100];                    char *msg;                    char sucess[]="Message from Ip Address:";                    int n;                    int des=0;                    int found;                    n=recv(fd,addr,sizeof(addr),0);                    addr[n]='\0';                    strtok_r (addr, "\n", &msg);                    found=search_addr(addr,&des);                    if ( found )                    {                        strcat(sucess,addr);                         send(fd,"Message Has been                                  sucessfully sended\n",36,0);                         strcat(sucess,"\n");                        strcat(sucess,msg);                        send(des,sucess,strlen(sucess),0);                     }                    else                    {                        send(fd,"Message Sending    Failed..\n",27,0);                    }                     sleep(5);                }            }        }        if ( minute == info->tm_min)        {            int j=0;            char Clients[1096];            memset( Clients, '\0', sizeof(Clients) );            sprintf(Clients,"Now Currently Available ip:\n");            for (j =0; j < client; j++)            {                strcat(Clients,p[j].clientAddr);                strcat(Clients," ");                strcat(Clients,p[j].name);                 strcat(Clients,"\n");              }            for ( j=0; j < client ; j++)            {                send(p[j].fd,Clients,strlen(Clients),0);            }            minute=minute+MINUTE;        }    }}

}

         void remove_client(int fd)      {int j=0;int pos;for  ( j=0; j< client ; j++){    if ( p[j].fd == fd )    {        pos=j;        break;             }            }for ( j=pos+1 ; j < client ; j++){    sscanf( p[j].name, "%s",p[pos].name);    p[pos].clientAddr=p[j].clientAddr;    p[pos].fd=p[j].fd;    pos++;}client--;i--;

} int search_addr(char address[],int *des) { char *name; int j; char temp_addr[100]; strcpy(temp_addr,address); strtok_r (temp_addr, " ", &name); for ( j=0; j< client ; j++ ) {

         if ( (strcmp(temp_addr,p[j].clientAddr)==0) &&          (strcmp(name,p[j].name)==0))    {        *des=p[j].fd;        return TRUE;    }}return FALSE;

}

Client.c

 #include <stdlib.h>    #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>       // #define  SERVERIP "192.168.12.61"       #define  PORT 5000    #include <setjmp.h>    #define MAXSLEEP 128     int main(int argc, char *argv[])        {int Response=1;int sockfd = 0, n = 0;char recvBuff[1024];struct sockaddr_in serv_addr; jmp_buf env;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(PORT); if(inet_pton(AF_INET, argv[1], &serv_addr.sin_addr)<=0){    printf("\n inet_pton error occured\n");    return 1;} setjmp(env);    if (connect_retry ( sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr) )< 0 ){    printf("Time Limited Exceeded....\n ");    return 0;} for (;;) {    char str[100];    char addr[100];    if ( Response == 1 )    {        int z = recv(sockfd,recvBuff,sizeof(recvBuff),0); //MSG_DONTWAIT        if ( z == -1 )        {        }        else if ( z == 0 )        {            printf("Server Failed ....\n");            longjmp(env, 2);            break;        }        else        {            recvBuff[z] = 0;            printf("'%s'",recvBuff);            sleep(1);        }    }    else    {        int z = recv(sockfd,recvBuff,sizeof(recvBuff),MSG_DONTWAIT); //MSG_DONTWAIT        if ( z == -1 )        {        }        else if ( z == 0 )        {            printf("Server Failed...\n");            longjmp(env, 2);            break;        }        else        {            recvBuff[z] = 0;            printf("'%s'",recvBuff);            sleep(1);        }    }    fd_set rfdset;    FD_ZERO(&rfdset);    struct  timeval tv;    tv.tv_sec = 10;    tv.tv_usec = 0;    FD_SET(STDIN_FILENO, &rfdset);    int bReady = select(STDIN_FILENO+1,&rfdset,NULL,NULL,&tv);    if (bReady > 0)    {        //  printf("Chat with Client Address: \n");        if( fgets (addr, 4096, stdin)!=NULL ) {        }        printf("Enter Message:\n");        if( fgets (str, 4096, stdin)!=NULL ) {        }        strcat(addr,str);        send(sockfd,addr,strlen(addr),0);    }    Response=0;}return 0;

}

int     connect_retry(int sockfd, const struct sockaddr *addr, socklen_t alen)      {int nsec;/* *          * Try to connect with exponential backoff. *                   */for (nsec = 1; nsec <= MAXSLEEP; nsec <<= 1) {    if (connect(sockfd, addr, alen) == 0) {        /*         *                          * Connection accepted.         *                                                   */        return(0);    }    /*     *                  * Delay before trying again.     *                                   */    printf("Waiting For Server....\n");    if (nsec <= MAXSLEEP/2)        sleep(nsec);}return(-1);

}

server send the ipaddress of new client connection and each few minutes 192.168.12.61 client1 ENter the msg Hello