Linux Socket Implementation of a Network Chat Room (Part 2): Independent Message Sending and Receiving Using Threads

1. Introduction

2. Code Implementation

1. Server Side

/*tcpserver.c  2011.9.1 by yyg*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <pthread.h> 

#define MYPORT 3490  // Define port
#define BACKLOG 10
#define MAXDATASIZE 1024 

int sockfd, new_fd;
pthread_t accthread, recthread;

void recmessage(void) {  // Function to receive client messages
    while(1) {
        int numbytes;
        char buf[MAXDATASIZE];
        if ((numbytes = recv(new_fd, buf, MAXDATASIZE, 0)) == -1) {
            perror("recv");
            exit(1);
        }
        buf[numbytes] = '\0';
        if (strcmp(buf, "exit") == 0) {  // If received message is "exit", terminate communication
            printf("Client is closed\n");
            close(new_fd);
            close(sockfd);
            exit(1);
        }
        printf("client:%s\n", buf);
    } /*while*/
}

void acceptconnect(void) {  // Function to accept client connection requests
    struct sockaddr_in their_addr;
    int sin_size;
    sin_size = sizeof(struct sockaddr_in);
    if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1) {
        perror("accept");
        exit(1);
    }
    printf("server: got connection from %s\n", inet_ntoa(their_addr.sin_addr));
    /* Create child thread for receiving messages */
    if ((pthread_create(&recthread, NULL, (void*)recmessage, NULL)) != 0) {
        printf("create thread error!\r\n");
        exit(1);
    }
}

int main(void) {
    struct sockaddr_in my_addr;

    /* Create socket */
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    /* Initialize parameters in sockaddr_in structure */
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(MYPORT);
    my_addr.sin_addr.s_addr = INADDR_ANY;
    bzero(&(my_addr.sin_zero), 8);

    /* Bind port and socket */
    if (bind(sockfd, (struct sockaddr*)&my_addr, sizeof(struct sockaddr)) == -1) {
        perror("bind");
        exit(1);
    }

    /* Listen for client socket connections */
    if (listen(sockfd, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }
    printf("listening...\n");

    /* Create child thread to accept connections */
    if ((pthread_create(&accthread, NULL, (void*)acceptconnect, NULL)) != 0) {
        printf("create thread error!\n");
        exit(1);
    }

    while(1) {
        char msg[MAXDATASIZE];
        scanf("%s", msg);
        if (send(new_fd, msg, strlen(msg), 0) == -1) {  // Send message to communicate with client
            perror("send");
            exit(1);
        }
        if (strcmp(msg, "exit") == 0) {
            printf("byebye\n");
            close(new_fd);
            close(sockfd);
            exit(1);
        }
    } /*while*/

    return 0;
} /*main*/

2. Client Side

/*tcpclient.c    2010.9.1 by yyg*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <pthread.h>
#include <netdb.h> 

#define PORT 3490
#define BACKLOG 10
#define MAXDATASIZE 1024 

int sockfd;
pthread_t recthread;

/* Function to receive messages */
void recmessage(void) {
    while(1) {
        int numbytes;
        char buf[MAXDATASIZE];

        if ((numbytes = recv(sockfd, buf, MAXDATASIZE, 0)) == -1) {
            perror("recv");
            exit(1);
        }
        buf[numbytes] = '\0';
        if (strcmp(buf, "exit") == 0) {
            printf("Server is closed\n");
            close(sockfd);
            exit(1);
        }
        printf("Server:%s\n", buf);
    } /*while*/
}

int main(int argc, char *argv[]) {
    struct hostent *he;
    struct sockaddr_in their_addr;

    /* Client input format: ./client 172.31.100.236
       If IP address is not provided, an error will be shown */
    if (argc != 2) {
        fprintf(stderr, "usage: client hostname\n");
        exit(1);
    }

    /* Get host IP address */
    if ((he = gethostbyname(argv[1])) == NULL) {
        herror("gethostbyname");
        exit(1);
    }

    /* Create socket */
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    /* Initialize sockaddr_in structure */
    their_addr.sin_family = AF_INET;
    their_addr.sin_port = htons(PORT);
    their_addr.sin_addr = *((struct in_addr *)he->h_addr);
    bzero(&(their_addr.sin_zero), 8);

    /* Send connection request to server */
    if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {
        perror("connect");
        exit(1);
    }

    /* Create child thread for receiving messages */
    if ((pthread_create(&recthread, NULL, (void*)recmessage, NULL)) != 0) {
        printf("create thread error!\r\n");
        exit(1);
    }

    /* Send messages. The same socket (sockfd) is used for both sending and receiving */
    while(1) {
        char msg[MAXDATASIZE];
        scanf("%s", msg);
        if (send(sockfd, msg, strlen(msg), 0) == -1) {
            perror("send");
            exit(1);
        }
        if (strcmp(msg, "exit") == 0) {
            printf("byebye\n");
            close(sockfd);
            exit(1);
        }
    } /*while*/

    return 0;
}

Execution Results:

Terminal 1:

[root@localhost net]# ./tcpserver
server:got connection from 172.31.100.236
Hello,World!
client:hello
client:xiaolian
client:iou
ok
exit
byebye

Terminal 2:

[root@localhost net]# ./tcpclient 172.31.100.236
Server:Hello,World!
hello
xiaolian 
iou
Server:ok
Server is closed