c windows connect（）失败。错误10049

Question

以下两段代码编译，但是我在客户端发生了一个connect() failed错误。 （由MinGW编译）。

客户端代码：

// thanks to cs.baylor.edu/~donahoo/practical/CSockets/code/TCPEchoClientWS.c 

#include <stdio.h> 
#include <winsock.h> 
#include <stdlib.h> 

#define RCVBUFSIZE 32 // size of receive buffer 

void DieWithError(char *errorMessage); 

int main(int argc, char* argv[]) 
{ 
    int sock; 
    struct sockaddr_in echoServAddr; 
    unsigned short echoServPort; 
    char *servIP; 
    char *echoString; 
    char echoBuffer[RCVBUFSIZE]; 
    int echoStringLen; 
    int bytesRcvd, totalBytesRcvd; 
    WSAData wsaData; 

    if((argc < 3) || (argc > 4)){ 
    fprintf(stderr, "Usage: %s <Sever IP> <Echo Word> [<Echo Port>]\n", argv[0]); 
    exit(1); 
    } 

    if (argc==4) 
    echoServPort = atoi(argv[3]); // use given port if any 
    else 
    echoServPort = 7; // echo is well-known port for echo service 

    if(WSAStartup(MAKEWORD(2, 0), &wsaData) != 0){ // load winsock 2.0 dll 
    fprintf(stderr, "WSAStartup() failed"); 
    exit(1); 
    } 

    // create reliable, stream socket using tcp 
    if((sock=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) 
    DieWithError("socket() failed"); 

    // construct the server address structure 
    memset(&echoServAddr, 0, sizeof(echoServAddr)); 
    echoServAddr.sin_family = AF_INET; 
    echoServAddr.sin_addr.s_addr = inet_addr(servIP); // server IP address 
    echoServAddr.sin_port = htons(echoServPort); 
    // establish connection to the echo server 
    if(connect(sock, (struct sockaddr*)&echoServAddr, sizeof(echoServAddr)) < 0) 
    DieWithError("connect() failed"); 

    echoStringLen = strlen(echoString); // determine input length 

    // send the string, includeing the null terminator to the server 
    if(send(sock, echoString, echoStringLen, 0)!= echoStringLen) 
    DieWithError("send() sent a different number of bytes than expected"); 

    totalBytesRcvd = 0; 
    printf("Received: "); // setup to print the echoed string 
    while(totalBytesRcvd < echoStringLen){ 
    // receive up to the buffer size (minus 1 to leave space for a null terminator) bytes from the sender 
    if(bytesRcvd = recv(sock, echoBuffer, RCVBUFSIZE-1, 0) <= 0) 
     DieWithError("recv() failed or connection closed prematurely"); 
    totalBytesRcvd += bytesRcvd; // keep tally of total bytes 
    echoBuffer[bytesRcvd] = '\0'; 
    printf("%s", echoBuffer); // print the echo buffer 
    } 

    printf("\n"); 
    closesocket(sock); 
    WSACleanup(); 

    exit(0); 
} 

void DieWithError(char *errorMessage) 
{ 
    fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); 
    exit(1); 
} 

服务器代码：

// thanks cs.baylor.edu/~donahoo/practical/CSockets/code/TCPEchoServerWS.c 

#include <stdio.h> 
#include <winsock.h> 
#include <stdlib.h> 

#define MAXPENDING 5 // maximum outstanding connection requests 
#define RCVBUFSIZE 1000 

void DieWithError(char *errorMessage); 
void HandleTCPClient(int clntSocket); // tcp client handling function 

int main(int argc, char **argv) 
{ 
    int serverSock; 
    int clientSock; 
    struct sockaddr_in echoServerAddr; 
    struct sockaddr_in echoClientAddr; 
    unsigned short echoServerPort; 
    int clientLen; // length of client address data structure 
    WSAData wsaData; 

    if (argc!=2){ 
    fprintf(stderr, "Usage: %s <Server Port>\n", argv[0]); 
    exit(1); 
    } 

    echoServerPort = atoi(argv[1]); 

    if(WSAStartup(MAKEWORD(2, 0), &wsaData)!=0){ 
    fprintf(stderr, "WSAStartup() failed"); 
    exit(1); 
    } 

    // create socket for incoming connections 
    if((serverSock=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP))<0) 
    DieWithError("socket() failed"); 

    // construct local address structure 
    memset(&echoServerAddr, 0, sizeof(echoServerAddr)); 
    echoServerAddr.sin_family = AF_INET; 
    echoServerAddr.sin_addr.s_addr = htonl(INADDR_ANY); // any incoming interface 
    echoServerAddr.sin_port = htons(echoServerPort); // local port 

    // bind to the local address 
    if(bind(serverSock, 
     (struct sockaddr*)&echoServerAddr, 
     sizeof(echoServerAddr) 
    )<0) 
    DieWithError("bind() failed"); 

    // mark the socket so it will listen for incoming connections 
    if(listen(serverSock, MAXPENDING)<0) 
    DieWithError("listen() failed"); 

    for (;;){ // run forever 
    // set the size of the in-out parameter 
    clientLen = sizeof(echoClientAddr); 

    // wait for a client to connect 
    if((clientSock = accept(serverSock, (struct sockaddr*)&echoClientAddr, 
       &clientLen)) < 0) 
     DieWithError("accept() failed"); 

    // clientSock is connected to a client 

    printf("Handling client %s\n", inet_ntoa(echoClientAddr.sin_addr)); 

    HandleTCPClient(clientSock); 
    } 

    // NOT REACHED 
} 

void DieWithError(char *errorMessage) 
{ 
    fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); 
    exit(1); 
} 

void HandleTCPClient(int clientSocket) 
{ 
    char echoBuffer[RCVBUFSIZE]; // buffer for echostring 
    int recvMsgSize; // size of received message 

    // receive message from client 
    if((recvMsgSize = recv(clientSocket, echoBuffer, RCVBUFSIZE, 0) <0)) 
    DieWithError("recv() failed"); 

    // send received string and receive again until end of transmission 
    while(recvMsgSize > 0){ 
    // echo message back to client 
    if(send(clientSocket, echoBuffer, recvMsgSize, 0)!=recvMsgSize) 
     DieWithError("send() failed"); 

    // see if there's more data to receive 
    if((recvMsgSize = recv(clientSocket, echoBuffer, RCVBUFSIZE, 0)) <0) 
     DieWithError("recv() failed"); 
    } 

    closesocket(clientSocket); // close client socket 
} 

我该如何解决这个问题？

Answer 1

你不初始化servIP：

servIP = argv[1]; 

我觉得你真的需要熟悉你的调试器，因为你应该已经能够发现这种错误在几秒钟内用调试器。

Answer 2

问题出在客户端。

1. servIP未被分配正确的值。你应该这样做

   servIP = argv [1];

在加载winsock2 dll之前。

2，这是recv（...）返回0的正常情况。它表示连接已关闭。