Linux socket 編程簡單例子

Linux socket 編程簡單例子

實例程序來自L L. Peterson & B S. Davie, Computer Networks: A System Approach, fifth edition, 第1.4節

client 端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define SERVER_PORT 5432
#define MAX_LINE 256

int 
main(int argc, char* argv[])
{
    FILE *fp;
    struct hostent *hp;
    struct sockaddr_in sin;
    char *host;
    char buf[MAX_LINE];
    int s;
    int len;

    if (argc==2) {
        host = argv[1];
    } else {
        fprintf(stderr, "usage: simplex-talk host\n");
        exit(1);
    }

    /* translate host name into peer's IP address */
    hp = gethostbyname(host);
    if(!hp) {
        fprintf(stderr, "simplex-talk: unkown host : %s\n", host);
        exit(1);
    }

    /* build address data structure */
    bzero((char*)&sin, sizeof(sin));
    sin.sin_family = AF_INET;
    bcopy(hp->h_addr, (char*)&sin.sin_addr, hp->h_length);
    sin.sin_port = htons(SERVER_PORT);

    /* active open */
    if ((s = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        perror("simplex-talk: socket");
        exit(1);
    }
    if (connect(s, (struct sockaddr*)&sin, sizeof(sin)) < 0) {
        perror("simplex-talk: connect");
        close(s);
        exit(1);
    }

    /* main loop */
    while (fgets(buf, sizeof(buf), stdin)) {
        buf[MAX_LINE-1] = '\0';
        len = strlen(buf) + 1;
        send(s, buf, len, 0);
    }
}

server端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define SERVER_PORT 5432
#define MAX_PENDING 5
#define MAX_LINE 256

int
main()
{
    struct sockaddr_in sin, csin;
    char buf[MAX_LINE];
    int len;
    int s, new_s;
    int on;

    /* build address data structure */
    bzero((char*)&sin, sizeof(sin));
    sin.sin_family = AF_INET;
//  sin.sin_addr.s_addr = inet_addr("127.0.0.1");;
    sin.sin_addr.s_addr = INADDR_ANY;
    sin.sin_port = htons(SERVER_PORT);

    /* setup passive open */
    if ((s = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        perror("simplex-talk: socket");
        exit(1);
    }

    /* enable address reuse */
    // http://www.ibm.com/developerworks/cn/linux/l-sockpit/
    on = 1;
    setsockopt( s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
    if ((bind(s, (struct sockaddr*)&sin, sizeof(sin))) < 0) {
        perror("simplex-talk: bind");
        exit(1);
    }
    listen(s, MAX_PENDING);

    /* wait for connection, then receive and print text */
    while(1) {
        if ((new_s = accept(s, (struct sockaddr*)&csin, &len)) < 0) {
            perror("simplex-talk: accept");
            exit(1);
        }
        while (len = recv(new_s, buf, sizeof(buf), 0)) {
            fputs(buf, stdout);
        }
        close(new_s);
    }
}

原書中程序的accept函數直接用sin做參數，運行時會出現錯誤；新建立一個sockaddr_in變量csin,傳給accept函數做參數，錯誤消失。