用TCP协议编写一个简单的服务器，客户端，服务器一直监听本机的6666端口。

server.cpp代码

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

constexpr int MAXLNE = 4096;

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

    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);

    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 (true) {
        if ((connfd = accept(listenfd, (struct sockaddr *)nullptr, nullptr)) == -1) {
            printf("accept socket error: %s(errno: %d)\n", strerror(errno), errno);
            continue;
        }
        n = recv(connfd, buff, MAXLNE, 0);
        buff[n] = '\0';
        printf("recv msg from client: %s\n", buff);
        close(connfd);
    }

    close(listenfd);
    return 0;
}

client.cpp代码

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

constexpr int MAXLNE = 4096;

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

    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;
    }

    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;
    }

    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, MAXLNE, 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;
}

makefile代码

all:server client
server:server.o
    g++ -g -o server server.o
client:client.o
    g++ -g -o client client.o
server.o:server.cpp
    g++ -g -c server.cpp
clinet.o:client.cpp
    g++ -g -c client.cpp
clean:all
    rm all

执行make命令,打开两个终端一个执行./server一个执行./client 127.0.0.1