前面文章，介绍了一个简单socket通讯Demo， 客户端和服务器进行简单的交互。两个代码都很简单，如果情况一复杂，就会出错。这节我们把代码完善一下，实现一个客户端输入，发送，服务器echo的交互。本文介绍客户端代码修改。

客户端其他函数修改同服务器端，可以看上一篇文章。

当服务器启动需要时间时， connect可能需要等待：

    int i = 60; //timeout, 60s.while (i){if (connect(sock, (SOCKADDR*)&sockAddr, sizeof(SOCKADDR)) == 0){break;}else{Sleep(1000);    //1s.--i;}}if (i == 0){std::cout << "connect error." << std::endl;closesocket(sock);sock = INVALID_SOCKET;return;}

这里等1分钟，如果服务器还是没起来，就退出了。

客户端的整个代码如下：

#include <iostream>
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <string>
#pragma comment(lib, "ws2_32.lib")#define SOCKET_ADDR "127.0.0.1"
#define SOCKET_PORT 1234void runSocketClient()
{SOCKET sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);if (sock == INVALID_SOCKET){std::cout << "socket error." << std::endl;return;}struct sockaddr_in sockAddr;sockAddr.sin_family = PF_INET;inet_pton(AF_INET, SOCKET_ADDR, &sockAddr.sin_addr.s_addr);sockAddr.sin_port = htons(SOCKET_PORT);int i = 60; //timeout, 60s.while (i){if (connect(sock, (SOCKADDR*)&sockAddr, sizeof(SOCKADDR)) == 0){break;}else{Sleep(1000);    //1s.--i;}}if (i == 0){std::cout << "connect error." << std::endl;closesocket(sock);sock = INVALID_SOCKET;return;}int ret = 0;char szBuffer[MAXBYTE] = { 0 };ret = recv(sock, szBuffer, MAXBYTE, NULL);if (ret == 0){std::cout << "recv == 0." << std::endl;closesocket(sock);sock = INVALID_SOCKET;return;}else{std::cout << szBuffer << std::endl;}while (1){memset(szBuffer, 0, MAXBYTE);std::string line;std::getline(std::cin, line);if (line.size() > MAXBYTE-1) {line = line.substr(0, MAXBYTE-1);}strncpy_s(szBuffer, line.c_str(), MAXBYTE);if (strncmp(szBuffer, "exit", MAXBYTE) == 0){break;}ret = send(sock, szBuffer, strlen(szBuffer) + sizeof(char), NULL);if (ret != strlen(szBuffer) + sizeof(char)){std::cout << "send error." << std::endl;continue;}else{std::cout << "send:" << szBuffer << std::endl;}memset(szBuffer, 0, MAXBYTE);ret = recv(sock, szBuffer, MAXBYTE, NULL);if (ret == 0){std::cout << "recv == 0." << std::endl;closesocket(sock);sock = INVALID_SOCKET;break;}else{std::cout << "recv:" << szBuffer << std::endl;}}if (sock != INVALID_SOCKET){closesocket(sock);sock = INVALID_SOCKET;}
}int main()
{WSADATA wsaData;WSAStartup(MAKEWORD(2, 2), &wsaData);runSocketClient();WSACleanup();return 0;
}

客户端测试：

connected.
hello
send:hello
recv:hello
123456
send:123456
recv:123456
exit