• client

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<errno.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#define MAXLINE 4096

int main(int argc, char** argv) {
    int   sockfd, n;
    char  recvline[4096], sendline[4096];
    struct sockaddr_in  servaddr;

    if (argc != 2) {
        printf("usage: ./client <ipaddress>\n");
        return 0;
    }

    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("create socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }
    printf("ip11:%s \n", argv[1]);
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(6666);
    if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0) {
        printf("inet_pton error for %s\n", argv[1]);
        return 0;
    }
    printf("[client][ip:%d, port:%d]\n", servaddr.sin_addr.s_addr, servaddr.sin_port);

    if (connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
        printf("connect error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }

    printf("send msg to server: \n");
    fgets(sendline, 4096, stdin);
    if (send(sockfd, sendline, strlen(sendline), 0) < 0) {
        printf("send msg error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }
    close(sockfd);
    return 0;

    char mbuf[30] = {0};
}

• server

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

#define MAXLINE 4096

int main(int argc, char** argv) {
    int  listenfd, connfd;
    struct sockaddr_in  servaddr;
    char  buff[4096];
    int  n;

    if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        printf("create socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(6666);
    printf("[server][ip:%d, port:%d]\n", servaddr.sin_addr.s_addr, servaddr.sin_port);
    if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1) {
        printf("bind socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }

    if (listen(listenfd, 10) == -1) {
        printf("listen socket error: %s(errno: %d)\n", strerror(errno), errno);
        return 0;
    }

    printf("======waiting for client's request======\n");
    while (1) {
        if ((connfd = accept(listenfd, (struct sockaddr*)NULL, NULL)) == -1) {
            printf("accept socket error: %s(errno: %d)", strerror(errno), errno);
            continue;
        }
        n = recv(connfd, buff, MAXLINE, 0);
        buff[n] = '\0';
        printf("recv msg from client: %s\n", buff);
        close(connfd);
    }
    close(listenfd);
    return 0;
}