Simple implementation of Linux multi-process CS Server

Linux multi-process CS Server simple implementation server side

• Multi-process Implementation multi-user connection, that is, each user a connection, here still with the server will receive the string to capitalize back to the client.
  • Code implementation

  #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <unistd.h> #include <ctype.h> #include <stdlib.h> #include <sys/wait.h> #define SERV_IP "    127.0.0.1 "#define Serv_port 8000void wait_child (int signo) {while (Waitpid (0, NULL, Wnohang) >0); return;} int main (int argc,char *argv[]) {pid_t pid;//process id int SFD, cfd;//receive connected SFD, and client communication cfd struct SOCKADDR_IN serv_a    DDR, clie_addr;//create server and client structure body socklen_t clie_addr_len;//client Structure body length char Buf[bufsiz], CLIE_IP[BUFSIZ];//BUF store received data int N, i;//read the number of data n, loop factor I sfd = socket (af_inet, sock_stream, 0);//Create Socket Bzero (&serv_addr, sizeof (SERV_ADDR));// Clear 0 serv_addr.sin_family = af_inet;//Set the protocol family to IPv4 serv_addr.sin_addr.s_addr = htonl (Inaddr_any);    Set the NIC to any valid local Nic//inet_pton (Af_inet, Serv_ip, &serv_addr.sin_addr.s_addr); Serv_addr.sin_port = htons (serv_port);//Set port bind (SFD, (struct sockaddr *) &serv_addr, sizeof (SERV_ADDR));//Set socket with SFD Association listen (SFD, 128);//sets the maximum number of outstanding accept. Start listening. while (1)//loop receive Client connection {Clie_addr_len = sizeof (CLIE_ADDR);//Initialize client structure Body length cfd = accept (sfd, struct sockaddr *) &clie_addr, &clie_addr_len);//Receive Client Connection printf ("Client ip:%s, port:%d\n", Inet_ntop (Af_inet, &clie_addr        . sin_addr.s_addr, Clie_ip, sizeof (CLIE_IP)), Ntohs (Clie_addr.sin_port));            PID = fork ();//Create a new process if (pid< 0)//error {perror ("fork Error");        Exit (1);        } else if (PID = = 0)//child process {close (SFD);//child process first close parent process file descriptor break;        } else if (pid>0)//parent process {Close (CFD);//parent process first close child process file descriptor signal (SIGCHLD, wait_child); }} if (PID = = 0)//The following is the true business processing part of the child process {while (1)//loop processing client Business {n = Read (CfD, buf, Sizeo            F (buf));            if (n = = 0)//If Read returns 0 indicating that the client has disconnected {close (CFD);//Close the client file descriptor return 0;   }         else if (n = =-1)//error {perror ("read error");            Exit (1);                } else {write (Stdout_fileno, buf, N);                for (i= 0; i< n;++i) {Buf[i] = ToUpper (Buf[i]);            } write (CfD, buf, N); }}} return 0;}

Client Side

• Connect to the server side, send a string, print the string that is received (that is, the same function as the NC command).
  • Code implementation

  #include <stdio.h>#include <string.h>#include <unistd.h>#include <netinet/in.h>#include <arpa/inet.h>#define MAXLINE 8192#define SERV_PORT 8000int main(int argc,char *argv[]){    struct sockaddr_in servaddr;    char buf[MAXLINE];    int sockfd, n;    sockfd = socket(AF_INET, SOCK_STREAM, 0);    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);    servaddr.sin_port = htons(SERV_PORT);    connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));    while(fgets(buf, MAXLINE, stdin)!=NULL)    {        write(sockfd, buf, strlen(buf));        n =Read(sockfd, buf, MAXLINE);        if(n ==0)        {            printf("the other side has been closed.\n");            break;        }        else             write(STDOUT_FILENO, buf, n);    }    close(sockfd);    return 0;}

Test results

• You can implement multiple clients to connect to the server at the same time, the server creates a child process per customer, and the process is automatically reclaimed by the parent process after the client disconnects.

There is a problem

• Without error handling, interference may occur when a multiuser connection is made.

Simple implementation of Linux multi-process CS Server