服务器端

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

#define SERVER_PORT 8888
#define BACKLOG     10

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

    int iSocketServer;
    int iSocketClient;
    int iRet;
    int iAddrLen;
    int iClientNum = -1;
    int iRecvLen;
    unsigned char ucRecvBuf[1000];
    
    struct sockaddr_in tSocketServerAddr;
    struct sockaddr_in tSocketClientAddr;

    /** 主进程关闭，子进程也关闭 */
    signal(SIGCHLD, SIG_IGN);

    iSocketServer = socket(AF_INET, SOCK_STREAM, 0);
    if (iSocketServer == -1) {
        printf("socket error!\n");
        return -1;
    }
    tSocketServerAddr.sin_family      = AF_INET;
    tSocketServerAddr.sin_port        = htons(SERVER_PORT); /** 将整型变量从主机字节顺序转变成网络字节顺序 */
    tSocketServerAddr.sin_addr.s_addr = INADDR_ANY; /** 本机所有IP */
    memset(tSocketServerAddr.sin_zero, 0, 8); /** 初始化tSocketServerAddr.sin_zero 8位数据都为 0 */
    /** 绑定端口号 */
    iRet = bind(iSocketServer, (const struct sockaddr *)&tSocketServerAddr, sizeof(struct sockaddr));
    if (iRet == -1) {
        printf("bind error!\n");
        return -1;
    }
    /** 监听 */
    iRet = listen(iSocketServer, BACKLOG);
    if (iRet == -1) {
        printf("listen error!\n");
        return -1;
    }

    while (1) {
        iAddrLen = sizeof(struct sockaddr);
        /** 客户端连接 */
        iSocketClient = accept(iSocketServer, (struct sockaddr *)&tSocketClientAddr, &iAddrLen);
        if (iSocketClient != -1) {
            iClientNum ++;
            /** net_ntoa 函数将 internet 网络地址、Ipv4 转换为 Internet 标准点十进制格式的 ASCII 字符串。 */
            printf("Get connect from client %d : %s\n",  iClientNum, inet_ntoa(tSocketClientAddr.sin_addr));
        }
        if (!fork()) {
            while (1) {
                /** 接收数据 */
                iRecvLen = recv(iSocketClient, ucRecvBuf, 999, 0);
                if (iRecvLen <= 0) {
                    close(iSocketServer);
                    return -1;
                } else {
                    ucRecvBuf[iRecvLen] = '\0';
                    printf("Get Msg From Client %d: %s\n", iClientNum, ucRecvBuf);
                }
            }
        }
    }
    close(iSocketServer);
	return 0;
}

客户端

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

/* socket
 * connect
 * send/recv
 */
#define SERVER_PORT 8888

int main(int argc, char **argv) {
    int iSocketClient;
    int iRet;
    int iSendLen;
    unsigned char ucSendBuf[1000];

    struct sockaddr_in tSocketServerAddr;

    iSocketClient = socket(AF_INET, SOCK_STREAM, 0);

    tSocketServerAddr.sin_family = AF_INET;
    tSocketServerAddr.sin_port = htons(SERVER_PORT);

    if (argc != 2)
	{
		printf("Usage:\n");
		printf("%s <server_ip>\n", argv[0]);
		return -1;
	}

    if (0 == inet_aton(argv[1], &tSocketServerAddr.sin_addr)) {
        printf("connect error!\n");
        return -1;
    }
    memset(tSocketServerAddr.sin_zero, 0, 8);

    iRet = connect(iSocketClient, (const struct sockaddr *)&tSocketServerAddr, sizeof(struct sockaddr));
    if (iRet == -1) {
        printf("connect error!\n");
        return -1;
    }

    while (1) {
        if (fgets(ucSendBuf, 999, stdin)) {
            iSendLen = send(iSocketClient, ucSendBuf, strlen(ucSendBuf), 0);
            if (iSendLen <= 0) {
                close(iSocketClient);
                return -1;
            }
        }
    }
    close(iSocketClient);
    return -1;
}