Linux 网络编程（TCP）

• 客户端代码

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

int main(int argc, char** argv){

    int socketfd = ;
    char sendbuf[];
    char recvbuf[];
    struct sockaddr_in server_addr;
    int port = ;
    int nbytes;

    if((socketfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == ){
        fprintf(stderr, "socket Error:%s\n\a", strerror(errno));
        exit();
    }

    bzero(&server_addr, sizeof(struct sockaddr_in));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    if((connect(socketfd, &server_addr, sizeof(server_addr))) == -){
        fprintf(stderr, "connect Error:%s\n\a", strerror(errno));
        exit();
    }

    while(){

        nbytes = recv(socketfd, recvbuf, sizeof(recvbuf), );
        recvbuf[nbytes] = '\0';

        printf("recv data is:%s\n",recvbuf);

        printf("Input:");
        scanf("%s", sendbuf);

        send(socketfd, sendbuf, sizeof(sendbuf), MSG_NOSIGNAL);
    }

    close(socketfd);

    exit();
}

• 服务器端代码

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

int main(int argc, char** argv){
    int old_fd,new_fd;
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;
    char recvbuf[];
    int port = ;
    int len,nbytes;

    if((old_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == ){
        fprintf(stderr, "socket Error:%s\n\a", strerror(errno));
        exit();
    }

    bzero(&server_addr, sizeof(struct sockaddr_in));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    server_addr.sin_addr.s_addr =  htonl(INADDR_ANY);

    if((bind(old_fd, &server_addr, sizeof(server_addr))) == -){
        fprintf(stderr, "bind Error:%s\n\a", strerror(errno));
        exit();
    }

    //listen的第二个参数backlog为内核缓存队列长度，该队列针对每个监听套接字包含两个队列：
    //一是未完成三次握手的，二是完成三次握手的
    if(listen(old_fd, ) == -){
        fprintf(stderr, "listen Error:%s\n\a", strerror(errno));
        exit();
    }

    while(){
        len = sizeof(struct sockaddr_in);
        if ((new_fd = accept(old_fd,
            (struct sockaddr *)&client_addr,
            &len)) == -) {
            fprintf(stderr, "Accept error:%s\n\a", strerror(errno));
            exit();
        }

        while(){
            if (send(new_fd, "hello fredric", strlen("hello fredric"), MSG_NOSIGNAL) == -) {
                fprintf(stderr, "send error:%s\n", strerror(errno));
                exit();
            }

            nbytes = recv(new_fd, recvbuf, sizeof(recvbuf), );
            recvbuf[nbytes] = '\0';

            printf("recv data is:%s\n",recvbuf);
        }

        close(new_fd);
    }

    close(old_fd);
    exit();
}