网络编程 tcp(一)

server端：

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

#define MAX_BUFF_SIZE 1024

int main(int argc, char *argv[])
{
    int ret;
    int listenfd, connfd;
    struct sockaddr_in server_addr;
    int client_len;
    struct sockaddr_in client_addr;
    char buff[MAX_BUFF_SIZE];

    listenfd = socket(AF_INET, SOCK_STREAM, );
    if (listenfd == -) {
        perror("socket()");
        return -;
    }

    memset(&server_addr, , sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons();
    ret = bind(listenfd, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if (ret == -) {
        perror("bind()");
        return -;
    }

    ret = listen(listenfd, );
    if (ret == -) {
        perror("listen()");
        close(listenfd);
        return -;
    }

    while () {
        connfd = accept(listenfd,(struct sockaddr *)&client_addr, &client_len);
        if (connfd == -) {
            perror("accept()");
            continue;
        }

        memset(buff, , sizeof(buff));
        recv(connfd, buff, sizeof(buff), );
        printf("%s\n", buff);

        memset(buff, , sizeof(buff));
        strcpy(buff, "hello, client---<from server>");
        send(connfd, buff, strlen(buff)+, );

        close(connfd);
    }

    close(listenfd);

    return ;
}

client端：

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

#define MAX_BUFF_SIZE 1024

int main(int argc, char *argv[])
{
    int ret;
    int sockfd;
    struct sockaddr_in server_addr;
    char buff[MAX_BUFF_SIZE];

    memset(&server_addr, , sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    server_addr.sin_port = htons();

    while () {
        sockfd = socket(AF_INET, SOCK_STREAM, );
        if (sockfd == -) {
            perror("socket()");
            return -;
        }
        ret = connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr));
        if (ret == -) {
            perror("connect()");
            return -;
        }

        memset(buff, , sizeof(buff));
        strcpy(buff, "hello, server---<from client>");
        ret = send(sockfd, buff, strlen(buff), );
        if (ret == -) {
            perror("sendto()");
            break;
        }

        memset(buff, , sizeof(buff));
        ret = recv(sockfd, buff, sizeof(buff), );
        if (ret == -) {
            perror("recv()");
            break;
        }

        printf("%s\n", buff);

        close(sockfd);

        sleep();
    }

    return ;
}

遇到的问题：

1.设置server地址时，server、client端都没有设置 sin_family，此时 client 调用 send 之后进程就直接exit掉了，没有返回。

2.client端必须要关闭掉fd之后重新socket一个，否则会报

　　Transport endpoint is already connected

错误。