FreeBSD上实现TCP网络编程

示例展示在FreeBSD系统上使用TCP网络编程，包括创建socket、bind、listen、accept、read、write等功能的实现过程。

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

#define SERV_PORT 9877
#define MAXLINE   4096

int main(int argc, char **argv)
{
    int                 listenfd, connfd;
    socklen_t           clilen;
    char                buf[MAXLINE];
    struct sockaddr_in  servaddr, cliaddr;

    if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        fprintf(stderr, "socket error: %s\n", strerror(errno));
        exit(1);
    }

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family      = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port        = htons(SERV_PORT);

    if (bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) == -1) {
        fprintf(stderr, "bind error: %s\n", strerror(errno));
        exit(1);
    }

    if (listen(listenfd, 1024) == -1) {
        fprintf(stderr, "listen error: %s\n", strerror(errno));
        exit(1);
    }

    while (1) {
        clilen = sizeof(cliaddr);
        if ((connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen)) == -1 ) {
            fprintf(stderr, "accept error: %s\n", strerror(errno));
            continue;
        }

        printf("connection from %s, port %d\n",
               inet_ntop(AF_INET, &cliaddr.sin_addr, buf, sizeof(buf)),
               ntohs(cliaddr.sin_port));

        while (1) {
            ssize_t n = read(connfd, buf, MAXLINE);
            if (n < 0) {
                fprintf(stderr, "read error: %s\n", strerror(errno));
                break;
            } else if (n == 0) {
                printf("client closed connection\n");
                break;
            }
            buf[n] = '\0';
            ssize_t nwritten = write(connfd, buf, strlen(buf));
            if (nwritten < 0) {
                fprintf(stderr, "write error: %s\n", strerror(errno));
                break;
            } else if (nwritten != n) {
                printf("short write (%ld/%ld)\n", nwritten, n);
            }
        }

        close(connfd);
    }
}

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