Linux 简单socket实现TCP通信

服务器端代码

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

int main( int argc, char *argv[] )
{
    int sockfd, new_fd;
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;
    int sin_size, portnumber;
    const char hello[] = "Hello!\n";
    if ( argc != 2 )
    {
        printf("Usage: %s portnumber\a\n", argv[0]);
        exit(1);
    }

    if ( (portnumber = atoi(argv[1])) < 0 )
    {
        printf("Usage: %s portnumber\a\n", argv[0]);
        exit(1);
    }

    /* 服务器端创建socket */
    if ( ( sockfd = socket(AF_INET, SOCK_STREAM, 0) ) == 1 )
    {
        printf("Socket Error !\n");
        exit(1);
    }

    /* 服务器端填充sockaddr结构 */
    bzero( &server_addr, sizeof(struct sockaddr_in) );
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(portnumber);

    /* 将本地地址与socket绑定 */
    if ( bind( sockfd, (struct sockaddr *)(&server_addr), sizeof(struct sockaddr) ) == -1 )
    {
        printf("Bind Error!\n");
        exit(1);
    }

    /* 进入监听模式 */
    if ( listen( sockfd, 5 ) == 1 )
    {
        puts("Listen Error!");
        exit(1);
    }

    while (1)
    {
        /* 服务器阻塞，直到与客户端建立连接 */
        sin_size = sizeof(struct sockaddr_in);
        if ( (new_fd = accept(sockfd, (struct sockaddr *)(&client_addr), (socklen_t *)&sin_size ) ) == -1 )
        {
            puts("Accept Error!");
            exit(1);
        }
        /* 连接成功 */
        printf("Server get connection from %s\n", inet_ntoa(client_addr.sin_addr) );
        inet_ntoa(client_addr.sin_addr);
        if ( write( new_fd, hello, strlen(hello) ) == -1 )
        {
            puts("Write Error!");
            exit(0);
        }

        /* 本次通信结束，循环下一个 */
        close(new_fd);
    }

    /* 关闭当前连接 */
    close(sockfd);
    return 0;
}

客户端代码

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

int main( int argc, char *argv[] )
{
    int sockfd;
    char buffer[1124];
    struct sockaddr_in server_addr;
    struct hostent *host;
    int portnumber, nbytes;
    if ( argc != 3 )
    {
        printf("Usage: %s hostname portnumber\n", argv[0] );
        exit(1);
    }

    if ( (host = gethostbyname(argv[1])) == NULL )
    {
        puts("Host Error!");
        exit(1);
    }

    if ( (portnumber = atoi(argv[2])) < 0 )
    {
        printf("Usage: %s portnumber\a\n", argv[0]);
        exit(1);
    }

    if ( ( sockfd = socket(AF_INET, SOCK_STREAM, 0) ) == 1 )
    {
        printf("Socket Error !\n");
        exit(1);
    }

    bzero( &server_addr, sizeof(struct sockaddr_in) );
    server_addr.sin_family = AF_INET;
　　 server_addr.sin_port = htons( portnumber );
    server_addr.sin_addr = *((struct in_addr *)host->h_addr);

　　 /* 与服务器建立连接 */
    if ( connect( sockfd, (struct sockaddr *)(&server_addr), sizeof(server_addr) ) == -1 )
    {
        puts("Connect Error!");
        exit(1);
    }

    if ( (nbytes = read(sockfd, buffer, 1024)) == -1 )
    {
        puts("Read Error!");
        exit(1);
    }

    buffer[nbytes] = '\0';
    printf("I have received: %s\n", buffer );
    close(sockfd);
    return 0;
}

运行结果